very, very generally, for a similar size fund with similar outperformance for both the fund and the analyst, the l/s equity guy will make more than the non-SSG/distressed credit guy. however, credit funds tend to be larger than a similarly staffed equity fund and have lower benchmarks so that's not really a fair comparison. obviously asset class performance matters year to year, one of the reasons most of the alternative asset manager have both equity and credit funds is diversification for the GPs, who have most of their net worth in the funds their company runs.

The answer is they wouldn't under that scenario, and for reasons to do with the immense variations in strategy, fund structure (both as it relates to fee loads and how P&L is attributed/paid out), and a million other factors, any trend that did exist would be functionally worthless for a given individual.

I don't feel that it's inherently "harder" to return x% at a credit fund versus an equity fund. Don't confuse returns of "the stock market" or "the bond market" with returns of actively managed investment portfolios, especially alternative credit strategies. Unless you're just passively investing in some theoretical capital structure the idea that debt has an inherently lower return than equity is just not really the case. Also, the breadth of the "credit" markets (cash, synthetic, structured, HY, IG, mortgages, sov/gov, distressed, etc) is so diverse that you can't generalize "credit" as one thing.

Some reasons include:
1) Leverage: Many/most hedge funds use leverage in one form or another (either embedded into the products they trade or via margin leverage) and credit products can often be levered more than equities.
A simple example:
Equity Fund Management LLC buys the stock market and returns 10% annualized over three years.
Credit Fund Management LLC buys the leveraged loan market which returns L+350 over three years. CFM borrows 3x times their capital at L+100. The return to their capital is L+1100.

2) The difference between interest rates and fixed income returns: If I tell you that the CDX.IG (synthetic investment grade index) pays 98bps, does that mean that my return from buying the index and holding it for a year will be 98 BPS? No! (Plus if I'm doing that, you shouldn't be paying me to manage your money).

3) carry trades and how they impact capital deployment: I was recently looking at a trade recommendation from a sell-side analyst that was essentially self-financing. It was a CDS curve trade. The fund putting on the trade received (imaginary numbers) 25 pts up front to buy 5 year protection and paid 10 pts upfront to buy 2 year protection. Assuming that the trade doesn't go against me and prompt a margin call I now have additional cash to invest in anything my prime broker will give me credit for.

4) Many funds (credit or equity) try to be market neutral, or at the very least least are not 100% long the market. Here is an example of what I mean:
Let's say that the stock market returns 12% next year and the HY bond market returns 7%. There are two funds that are both 100% long and 100% short. If neither fund's longs or shorts outperform, then both funds return zero. If both fund's longs outperform the market by 2% and their shorts match the market, they both return 2%, etc. This is an extreme example, most funds aren't actually at net-0% exposure, but part of the thesis behind going both long and short is that it removes beta and emphasizes the impact actual investment-selection.

As another point, two of the three things you list here (understanding the capital structure, going through legal docs, understanding the fundamentals of the business) are absolutely crucial to equity investing as well as debt. It's true that some fundamental credit strategies involve a lot of reading (bankruptcy filings and credit agreements etc) but so do fundamental equity strategies (industry research, channel checks, etc).