"You can always hold the shorter board sideways longer but you can't make the longer one spin faster than it wants to."-Silverfish User
I've ridden lots of wheelbases, but I have to say...while my friend's NS Admiral's 24" wb or my Sugar Kick's 22.5" may be a bit more difficult to drag out a long slide if inexperienced, the board will always do EXACTLY what you tell it to.
Ever stand on your evo and ask yourself why the pros can slide but no matter how hard you push your wheels don't leave buttery thane everywhere? Well...okay. That's probably not the Evo's fault, that's probably form.
Consider this: Why does tech sliding utilize such short boards? The answer lies in the short-boards wheelbase.
Now I'm not going to tell you "the shorter the WB, the better the wheelbase". What I AM going to tell you though, is that those Tech-slider riders use boards that they can FULLY control.
So if you're new to the sport, or even just a little unversed in the importance of wheelbase, I hope the following will help you.
Wheelbase: The distance from one set of wheels to the other (basically).
The shorter it is, the more responsive and agile. The longer it is, the opposite becomes more true.
Some argue that a shorter wheelbase is far less controlled and and rather awful to slide on. While I wont argue preferences, a rider is the only thing that controls a board, so if someone says "your board doesn't seem very controllable during a slide", what they mean is that they do not personally have the skill to control it. This reflects a common undertone of anything requiring skill: it's all in the rider.
Now, I'm not asking all of you to go out to your nearest shop and purchase a skateboard because of its ridiculously short wheelbase, but I think it could really help some of the newbies here to maybe look into trying a friend's board that has a shorter wheelbase and just try fumbling around with some 180s.
Longer wheelbases do have their benefits though. If you're completely new, the extra stability and cushion a longer WB will give is likely to encourage you to keep trying, and will allow you to make some mistakes while keeping you in their hammock.
A wheelbase guide on silverfish (the only source for the quotes) has some people in the comments section mentioning that a longer wheelbase is an easier starting point for beginners, and while I do not disagree, I must say that while downhilling/letting the board carry you through a slide may be easier on a longer wheelbase when you're just starting out, initiating a slide and learning exactly how to control your board before,during, and after a slide will be more easily achievable on a shorter WB.
I do not mean to say that a shorter board will always be what is better, as it really comes down to preference (the Evo is a fine example of this), but everyone who feels the stoke should experience both the gliding, hammocky mid-long size range of longboarding, and the devious, "uncontrollable" short WB size of longboarding.
Also note: A proper technique and some appropriate wheels will help you achieve your goal.
TL;DR: "shorter wheelbase is less forgiving, but has more control (often too much for some disciplines/people)", but really it comes down to preference.