RE20 has a very characteristic "EV Sound" that is similar and comparable to all the other EV dynamic mics. If you can find a used EV ND167, 357, 457, 757, 767, 967 that someone will let you borrow and test, then you will hear almost exactly what an RE20 sounds like. The 967 is far superior to those others, and will sound most like an RE20, but the RE20 will still sound better yet. The general tone and freq response will be similar, but the RE20 is bigger diaphragm and will be more clear and easier to get a good take with......assuming you have lots of clean gain. Its ability to almost nullify proximity effect is not intended to assist singers who dont have professional technique, it is intended for broadcasters who sit at a radio desk and eat the mic. The RE20 is first and foremost a broadcast mic, and it just happens to work well for a lot of studio apps. It is brighter and phatter in the upper mids, which some people like. It will never give you the same level of clarity or detail as a good condensor, but it will outpace any of the budget dynamics easily.
All that said, if you want a great dynamic that will help cancel out room noise, can be had used mint for $300 or less, is built well in the USA, and works great with a wide range of vocals, then you should skip the RE20 and start hunting for SM7b. There are basically 3 popular mics that fit that description, RE20, MD421, and SM7b. And the SM7b is by far (imo) the best one for vocals. I found mine mint condition on ebay from a private seller for $280, and I sold my RE20 within a week after I got the SM7. In fact, I have gotten rid of every EV mic I ever had. You dont realize what that characterisstic EV sound does to your mix until you work with it for awhile. But if you get an RE20 and never compare it to anything else, you'll never know what you're missin anyway! Not a bad mic, not at all, just not as good for vocs as the SM7.
Sibilance can also be defeated simply by changing the angle at which you face the mic. I cut my own sibilance way down instantly just by turning the mic away from my mouth about 45 degrees.
Now if you start talking kick drum mics, the story changes quickly!