Thats my point, they are functionally identical. The Mac version doesn't integrate into Mac OS X very well. There are a few pages floating around demonstrating this. From my experience, its a good Windows app with a very poor Mac OS X port.
Given I use all three operating systems (XP, Linux and MacOSX [both tiger and leopard for that matter on different partitions]), I guess I'm not so sensitive to OS-Centric quibbles.
Frankly, I hated Apple's keyboard that came with this PowerMac so I bought a Logitech one and swapped the command key to CTRL on it (seeing as how everything that uses CTRL in Windows OR Linux uses CMD in OSX...a case of Apple holding on to non-standards just to be difficult, IMO; it does then cause issues in X11 since my ALT key then does the CTRL stuff, but I don't use X11 much in OSX). If I hadn't changed anything, it would still have two keys reversed since the alt key is actually where the CMD (apple) key goes and the "windows" key is alt and CTRL would be CTRL on both EXCEPT that htey don't DO the same things (again that's CMD). Confused yet? You have to do SOMETHING when using a standard keyboard (i.e. not a crappy Apple one that is either missing the numeric keypad or has flat keys that remind me of a cross between a speak'n'spell and an ATARI 400 keyPADboard. Don't even get me going on that stupid Mighty Mouse design. I bought a cheap Dynex mouse and it works identical in both OSX and Windows now.
I guess what I'm getting at is Firefox REALLY not fitting into OSX or is more like OSX isn't fitting in with everyone else out there (i.e. Windows, Linux, BSD, etc.) You only think it's odd because you are used to Apple doing non-standard things (Appletalk, Nubus, pushing Firewire in lieu of USB 2.0 when it first came out instead of including both, etc.), which only ever happens in the first place because Apple wants you to buy THEIR hardware, not get a good deal on something standard and cheap from the rest of the computing world. They finally realized one button doesn't cut it (i.e. they were wrong all along about it) but to try and cover the fact up, they HIDE the second button on their mice even today. It works well enough to make some PC users think they STILL use one button. Well, then there's the absolutely ABSURD use of only ONE button on their laptops even today when not only are there right AND middle button clicks supported in OSX, but they are DESIGNED to be able to run Windows now either directly via BootCamp or in addition with Fusion or Parallels. So WHY would they still insist on pretending to use one button on a laptop when they know there are a LOT of people that want that 2nd button. Sure you can do that double tap on the pad or whatever, but it's no substitute for the real thing or they wouldn't include the first button either.
I digress. I'm sure given the extension system someone can use the Stylish extension or something like that to make every single key shortcut, button, etc. identical to Safari for those that need that for some reason. I mean Apple USED to depend on Internet Explorer so how between then and now everyone thinks Apple = Safari is beyond me, especially given how awful Safari was a couple of years ago compared to today. But as I mentioned earlier, the biggest difference between Safari and Firefox is that if I don't like Firefox's default interface, I CAN do something about it. With Safari, if I don't like it (say on my XP machine where it looks completely out of place), I'm stuck because Apple believes things have to look like their current method even on operating systems where NOTHING ELSE looks like that. But as someone else attempted to point out, you don't see die-hard Mac fans complaining how awful Safari looks on Windows, just Firefox3 (which at least makes an attempt to better fit in and can be further adapted by the user) which then gets hounded for its supposed sins against humanity.
Personally, I can use Firefox OR Safari and I don't feel all that weirded out with either one. There is, after all, more than one way to skin a cat, even a Leopard.