Higan is wayyy better. (fact, not opinion, fact).

No, Higan is not way better than snes9x in all situations. In particular, some drawbacks of Higan:
* It has high system requirements, particularly in terms of CPU. Hence, on some systems, Higan might run slowly.
* As a corollary to the above, it also uses more electricity. This is most noticeable on a laptop or other battery-powered device, where the battery won't last as long under Higan.
* There exist ROM hacks that do not work on Higan or recent versions of snes9x. For these hacks, you will need to use an older version of snes9x, or possibly even zsnes (probably itself under emulation these days), for them to work properly. (Note that these hacks will also fail if you try to run them on real hardware.)

Hi, sorry for my lack of knowledge but I wish to extract the rom from metal slug 4 to run in MAME. Is there a way I can do this?

Hello. This thread is long abandoned, but I've resurrected it here. In short, there is a way to extract the MS4 ROM (and many others), and I'm working on a guide for that bit, but it's not entirely easy and will most likely not run properly outside of Linux (or WSL).