VG-10 and S30V are similar steels on terms of toughness and edge retention. You're unlikely to notice a difference unless you go looking for one. There is no 'best steel.'
VG-10 is a Japanese steel, and S30V is a newer American powder steel. Both are technologically advanced and chemically complex, but are both more similar to each other than either steel is to say, 1095.
'Why they are worth it' is a sensitive question around here. People cite the knife's design and ergonomics, and I agree, but ultimately this is a matter of user preference. People cite the superior materials - S30V, phosphor-bronze and aerospace-grade titanium - but these materials all appear on knives from those other brands that you mention, Benchmade, Spyderco, etc. I can't say that Reeve knives are better, though I personally believe so. In my strict opinion, there are two things that make Reeve's knives as good as they are: the fit and finish, which is top-tier, and all the little hand-fitted details that go into every knife. Things like the pivot-bushing system on the Sebenza, or the perforated washers on the Umnumzaan, and a half-dozen other little details that I won't bother listing. Things that improve the function, and slow the wearing of the knife to an almost unnoticeable rate. At that level of fit and finish - which is close to within several thousandths of an inch - most of those things have to be done by hand, and aren't typically seen in knives from other companies. It's that hand-finished, hand-loved attention to detail that to me, makes Reeve's knives worth the price.
Lately the CRK owners on this board have been dealing with the exact same questions over and over, from people who are skeptical about CRKs and the price/value ratio.
All we ever say, albeit awkwardly and in many more words than this, is that we believe Reeve's knives are worth the price. Some people accept the advice, and some people keep arguing. Some people pull the trigger and buy a CRK, and some do not. Of those who do, most (in my experience) are impressed, and some are not.
Don't get me wrong, you ask a reasonable question, but very often such things have quickly degenerated into flame wars and pointlss, endless arguments. For that reason, I'm trying to be frank and delicate, to defuse those things before they happen.
If you like knives, and you have sufficient disposable income to spend on one of Reeve's pieces, I and others would suggest you go for it. The best case scenario is that the design, the F&F, and overall quality blow you away. The worst case scenario is that you are underwhelmed, in which case you can turn around and sell the knife for only slightly less than what you bought it for. One of the nice things about Reeve knives - and in my opinion, a testament to his design philosophy - is that they don't depreciate that much. People who spend $385 on a Sebenza, only to decide they don't like it, have been able to sell it for $300-$340.
Whether you like it or not - call me naive, but I'm betting you will - you will definitely stop wondering whether they're for you or not.
If you decide not to go for a Reeve knife, then the other brands that you mentioned, Benchmade, Spyderco, Kershaw and others, have produced outstanding knives as well, and will likely suit you just fine.
Good luck.
