Spectacular work by design chief Ian Callum -- and drastically improved quality -- has made Jaguar a surprising global luxury contender, and its corporate parent Tata Motors an intriguing investment. Source: Jaguar Land Rover.

Many experts say the global auto business will change more in the next 15 years than it has in the last 50, as new trends such as autonomous cars, electric propulsion, and the rise of crowdsourced mobility combine to offer unprecedented challenges and opportunities to the world's automakers.

Tesla Motors has drawn a great deal of attention from investors, thanks to its innovative electric luxury sedans and the compelling vision of CEO Elon Musk. But it's not yet time to count out the global automakers. Our Motley Fool contributors think there are good reasons to own the best of the established auto giants as we move into this period of dramatic change. 

Here are three views on the best big-automaker stocks to own now.

Asit Sharma: For a long-term holding that will benefit from global growth trends, consider Tata Motors Limited (TTM). Tata is the leading automobile manufacturer on the Indian subcontinent, sporting annual revenues of $39 billion, and a handsome net profit margin of 7%. The company is well positioned to take advantage of the vibrant Indian economy, as it's focused in recent years on building compacts and subcompacts with affordable price points to attract new entrants into India's burgeoning middle class.

Tata also manufactures light, medium, and heavy commercial vehicles for both the Indian and wider Asian markets -- these make up about 42% of total production. Moreover, the company is a global concern, having purchased Jaguar Land Rover from Ford (F 0.69%) in 2008.

Due to this "barbell" strategy of offering lower-margin consumer and commercial vehicles in Asia, alongside promotion of two revered luxury brands worldwide, Tata has a clear path to revenue and profit expansion for the foreseeable future. But the journey won't lack for challenges. Tata's stock is currently down 21% year to date, due largely to foreign currency pressures on earnings, as well as investors' unease at higher than anticipated costs as the Jaguar Land Rover division builds its presence in the Chinese luxury automobile market.

Against both near- and long-term challenges, Tata relies on a bedrock of truly impressive cash flow -- the company booked $6.2 billion in operating cash flow in 2014. Currently, management is directing nearly all excess cash into investment projects, such as a Jaguar Land Rover production facility in Rio de Janeiro, which will have capacity to supply 24,000 luxury vehicles annually to the Brazilian market when it comes online in 2016.

I believe the current swoon in TTM presents an excellent opportunity for savvy investors. Tata trades at just 6.4 times forward earnings, making it cheaper than even perennially undervalued, larger peers Ford and General Motors (GM 1.20%). For those who can stomach a little volatility and have a long investment horizon, attractively valued Tata Motors is one of the best positioned stocks for global growth in the automotive industry. 

Rich Smith: Over my lifetime, I've owned trucks from GMC and from Chevy, and cars from Nissan and Honda. But which automotive company would I want to own stock in?

That's Ford, hands down.

Why? Simple. The single most important thing to me, when choosing a stock to invest in, is finding a company that generates strong cash profits. Within the car industry, no one generates as much cash as Ford.

The all-new 2015 F-150 was a big gamble for Ford. It looks set to pay off handsomely in the second half of 2015. Source: Ford Motor Co.

Over the past 12 months, S&P Capital IQ data show Ford Motor Co. generating $6.95 billion in positive free cash flow (operating cash flow minus capital expenditures). That's twice the free cash flow that Honda produces and more than twice Toyota's output. It's five times Fiat Chrysler's free cash flow number, and infinitely better performance than what we see at cash-burning Nissan and General Motors.

With Ford trading for just 8.5 times free cash flow and paying its shareholders a 4% dividend yield, I'd happily buy shares of Ford stock if it were projected to grow earnings at just 4.5% annually. In fact, Capital IQ data shows that most analysts foresee 22.7% annualized earnings growth at Ford over the next five years.

That number may be overly optimistic, but the fact that even the most pessimistic analysts following Ford paint a worst-case scenario of 15% annualized earnings growth tells me that there's a big margin of safety in Ford stock today.

Now that I've pointed this out to you, Fool disclosure rules forbid me from trading in Ford stock for at least the next three days. But I have to admit -- after taking a close look at the numbers today, I'll be thinking very hard about doing some buying three days from now.

John Rosevear: Like Rich, I'm a big fan of Ford and of its prospects over the next few years. (Unlike Rich, I already own Ford shares.) But I'm also a fan and shareholder of General Motors, and I think the General might have the more compelling investment story right now. 

To be clear, I agree with Rich that Ford has the better-looking cash flow right now. But the investment case for GM really is more about the "story" than it is about GM's financials as they are today. 

For decades, the story around GM has been one of epic mismanagement and squandered opportunities. That story keeps many investors from taking a closer look at the company, but here's the thing: It's an old story. 

When's the last time a Chevrolet Impala was a favorite of Consumer Reports? Like other recent GM products, this big sedan is a strong, well-executed contender. Source: General Motors.

Under CEO Mary Barra, GM is writing a new and very different story. Its latest products are winning over veteran reviewers and scoring big victories in quality surveys. Its financial goals and reports are straightforward, open, and sensible -- a sea change from the old days. 

But the best may be yet to come -- and that's what makes GM an intriguing buy right now. Last fall, Barra and her senior team rolled out a compreh ensive plan to boost GM's adjusted pre-tax profit margin to between 9% and 10% by early next decade. (It was 5.8% in the first quarter.)

The plan has several key components, including an aggressive new-product cycle, a massive overhaul and expansion of the high-profit Cadillac brand, big investments to maintain and expand on GM's already-huge position in China, and a slew of internal and procedural changes intended to let GM take full advantage of its massive global scale (something that global archrivals Toyota and Volkswagen both do very well.)

Barra has joked that GM isn't interested in merging with Fiat Chrysler because it's still working on merging with itself. The truth behind that joke is that GM has a lot of potential yet to be fully harnessed.

Her plan will harness it. It's a good, sensible, aggressive plan, and the progress that GM has already made over the last few years (much of it driven by Barra and her senior team in their prior roles) makes it a credible one.  If it works, GM's profits and share price will see big jumps from current levels.