I have used both Go (extensively) and V (not so much). Go's cross compilation, concurrency support, GC & stability are much better than V's. V compiles much much faster in spite of generating C (unless you use clang), plays better with C, its syntax choices seem better (default to const, less onerous error handling, sum types, option type, not relying on Capitalization for exporting etc.), optional GC (though far from perfect), etc. I can see writing an OS in V (but not in Go). I am in two minds about whether it should try to simulate concurrency like Go does (goroutines are coroutines, mapped to system threads only for blocking syscalls) as that might not be the right choice for kernel level code.

V hasn't had the resources or backing that Go continues getting. Most of its work is done by volunteers. AFAIK it hasn't had the benefit of the experience of multiple world class programmers like Go's designers. Good language design also involves leaving out features and that involves discussing or experimenting with such features. IMHO V can use more of that. But so far I like a lot of what I see in V.