3D printing can now produce chess pieces, turbines, and even model hearts. Photo sources, from left: John Abella via Flickr, Fool.com, Wikipedia.  

Between 2010 and the beginning of last year, any stock remotely associated with 3D printing shot through the roof. For no company was that more evident than 3D Systems: Over that time frame, shares zoomed 2,290% higher. However, although I own a small amount of the company, it's not 3D Systems stock that will be getting my money in 2015. It is, instead, Stratasys (NASDAQ:SSYS) stock.

Let me explain why...

There may only be a few winners
According to industry review and forecast Wohlers Report 2014, 3D printing is going to enjoy tremendous growth over the next six years: The industry is expected to grow by an astounding 31% per year until at least 2020. That might make the average investor believe that just about any company can profit from getting in on the game now.

But as fellow Fool Steve Heller demonstrated in a brilliant piece last week, the exact opposite may be true. "Given the industry's strong growth trajectory, likelihood of increasing competition, key patents expiring, and threat of technological disruption, investors shouldn't rule out the possibility that profits may be difficult to come by for 3D printing companies in the long run." 

Those are strong words coming from one of the Motley Fool's 3D printing specialists. And they make sense: When patents expire in a high-growth industry, the barriers to entry are low, and prices for printers and consumables can be pushed down in short order.

So what makes me so confident in buying Stratasys stock?

Investing in the future
Unlike 3D Systems, Stratasys has historically taken a slow, steady, and measured approach to acquisitions. The company has made two big splashes: the merger with Objet -- which gave it access to new industries and technologies -- and the acquisition of Makerbot -- one of the fastest-growing consumer brands of 3D printers.

In these cases, Stratasys realized superior products that it couldn't compete with on its own, and decided to join forces.

Of course, the company can't keep up that strategy forever -- it would eventually go bankrupt from spending all of its money on acquisitions.

But that's why I like to see Stratasys increasing its research and development budget by leaps and bounds.

Here's why this is so crucial: When any company could come along with a game-changing idea, upstarts can have a huge advantage. The one variable that Stratasys has -- which upstarts don't -- is a war chest of $460 million. By spending that cash on R&D, the company is able to attract the brightest minds in the field, and do everything it can to maintain a technological edge on the competition.

A solid foundation for Stratays stock
Moreover, Stratasys has the largest base of installed 3D printers in the world at roughly 110,500. That's crucial, because the printers themselves are relatively low-margin. This is a classic razor-and-blades model. It is from the consumables -- the materials that people need to order from Stratasys to make their printers work -- that Stratasys makes high-margin, recurring sales.

The more printers the company is able to sell now, the more cash that will be coming in for it down the road, which it can invest back into R&D and create even greater distance between itself and the competition.

The price for Stratasys stock: Lower than you might imagine
Figuring out how to value Stratasys can be a little difficult, since the company's financials became jumbled when it merged with Objet. Using non-GAAP measures, which I think is fair in this case, Stratasys stock looks like a better deal now than it has been for quite some time.

Not since the end of the first quarter of 2012 -- three years ago -- has Stratasys stock been so cheap. In fact, the company is about half the price -- based on P/E -- than it was just one year ago. The amazing thing is that Stratasys is fundamentally a stronger company: Earnings have grown by 28% per year over the last three years -- on a non-GAAP basis.

Combine these factors -- a comparatively cheap price, a large base of installed printers that should provide stable income, and a serious investment in the future -- and you can see why I plan on making Stratasys stock a larger personal holding in 2015.