I use both. (Especially since Google started only allowing you to login to one gmail session at once, but I used both before that.) Currently there are about three things that keep me from using Chrome entirely, because I do think it's a better overall browser but not better for my particular use case.
The first is lack of the Tree Style Tabs extension (in general lack of extensions was my biggest problem with Chrome until recently; now they have NoScript and AdBlock and ctrl+shift+j is about as good as FireBug which were the deal-breakers for me before), the second is not eating up huge amounts of memory if I have 593 tabs loaded into it (which is currently what I have on this Firefox), the third is I don't like their URL box. Firefox's AwesomeBar is almost perfect, I just wish it had better coverage of my history+favorites (I'm sure there's an about:config option somewhere that tunes it).
The first is lack of the Tree Style Tabs extension (in general lack of extensions was my biggest problem with Chrome until recently; now they have NoScript and AdBlock and ctrl+shift+j is about as good as FireBug which were the deal-breakers for me before), the second is not eating up huge amounts of memory if I have 593 tabs loaded into it (which is currently what I have on this Firefox), the third is I don't like their URL box. Firefox's AwesomeBar is almost perfect, I just wish it had better coverage of my history+favorites (I'm sure there's an about:config option somewhere that tunes it).