Many gold stocks have been picking up steam, what with gold prices having delivered more than 15% gains so far this year. Not all in the space have kept pace with the yellow metal's rally though, and notable names like Eldorado Gold (NYSE:EGO), McEwen Mining (NYSE:MUX), and Harmony Gold (NYSE:HMY) are lagging the metal by huge margins.

Investors are now wondering whether these beaten-down gold stocks are best avoided, or if the time is ripe to scoop up their shares before they surge and catch up with the precious metal. To answer that question, you have to dig deeper into what's brewing inside each of these three gold miners. And if you do, you'll realize why two are best avoided, but one may be a bargain buy today.

Eldorado Gold: It's in a tough spot

2017 is pouring bad news for Eldorado Gold from all sides. Shares of the Canadian miner started losing ground rapidly after May when it announced plans to acquireIntegra Gold.

A dice with buy on it beside a stack of gold coins

Is now the time to buy beaten-up gold stocks? Image source: Getty Images

While Eldorado's rationale that Integra's projects -- such as Lamaque, with an annual production potential of 123,000 ounces of gold at all-in-sustaining cost (AISC) as low as $634 per ounce -- will give it significant headway in the high-potential province of Quebec holds water, the hefty premium that Eldorado paid for Integra didn't sit well with investors.

EGO Chart

EGO data by YCharts

Just as the market was trying to digest the Integra move, the Greek government announced arbitration proceedings against Eldorado to settle long-pending disputes over the miner's developing projects including Skouries and Olympias mines in northern Greece. Eldorado has made a substantial bet on its projects in the country, so an adverse decision could deal a huge blow to its growth prospects.

The arbitration could last several months, and even if Eldorado comes out a winner, a delay in the start-up of its mines -- especially the high profile Skouries -- is highly likely. That would also mean a longer wait for investors to see Eldorado turn free cash flow positive. The risk is substantial, and investors may be better off staying on the sidelines unless there's some positive news from Greece.

Harmony Gold: Where are the growth catalysts?

2016: Harmony Gold doubled in value to emerge as one of the top performing gold stocks.

2017 so far: Harmony Gold is at the bottom of the list of gold stock performers, having lost roughly 8% year to date and a whopping 44% in the past 12 months.

This reversal of fortunes didn't happen without reason.

It started with a strike at one of Harmony's mines in March that lasted nearly two weeks. Investors were already jittery about the effects of the strike, and as well as Harmony's gold hedges, which started to roll off in April, when the miner dropped another bombshell. In August, the miner reported  a 66% slump in its earnings per share for its fiscal 2017, which ended June 30 -- a decline it attributed in part to asset impairments and provisions for a possible class action suit. Equally bad, Harmony's AISC came in nearly 18% higher year over year at $1,182 per ounce, placing the company at the higher end of the industry cost curve.

In short, Harmony's headwinds are plentiful, and growth will be hard to come by if gold prices cool down. The miner might be doing its bit to strengthen its balance sheet, but I'll need better visibility on its production growth and costs before I could get excited about the stock.

McEwen Mining: Changing its production drivers

McEwen Mining started the year with a bang, but decelerating production cut short its rally. The problem is, McEwen only turned its first profit last year. That milestone, however, comes with a caveat: McEwen's primary mine, El Gallo 1 in Mexico, is nearing the end of its life, which means the miner's profitability now depends entirely on how quickly and efficiently it can fill the El Gallo production gap.

Of course, McEwen isn't sitting on its hands. Its El Gallo 2 project is in the advanced stages of development, its Gold Bar project in Nevada is on track, and it's making big strides in the Timmins gold camp in Canada, having recently struck a deal with  Primero Mining to acquire its Black Fox complex. That followed close on the heels of McEwen buying out Lexam, which has several projects in the region.

If El Gallo 2 and Gold Bar remain on track, McEwen's gold production could nearly double in 2019 from its expected 2018 base.

Chart showing McEwen Mining's gold production from 2012 to 2020 expected.

Image source: McEwen Mining

Note that this forecast doesn't include the output from Timmins. Also, McEwen's latest assessment for the Los Azules copper project in Argentina pegs its internal rate of return to be an impressive 20.1%. While that mine is still some years away from production, it could become one of McEwen's most valuable assets in the future.

Given the backdrop, aggressive investors looking for exposure to gold may want to bet on McEwen today.

Neha Chamaria has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.