I probably wasn't clear enough, but - the only thing iOS 4.3.5 did was to fix a security issue (per Apple). And, iOS 4.3.4 came out to fix another security hole (the one c0mex was able to exploit to jailbreak).
AFAIK, that's the only reason for those 2 versions. So, if fixing Apple-noted security issues is not important to you, then no, there is no need for you to update.
IOW, you'll see no change if you do update to IOS 4.3.5
Hope that clrifies things better.
Marilyn