HRAP ex uses a sanwa stick and hori buttons.
HRAP ex SE uses all seimitsu parts. seimitsu sticks are stiffer (no homo) than sanwa jlf sticks and have a shorter throw. and seimitsu buttons are like hori buttons but of much higher quality. they both offer a little resistance and click when you press them and are not as sensitive as sanwa buttons. here’s a great vid of desk using seimitsu buttons. you can hear the clicks and see how they offer a little resistance. i am not sure what stick he uses.
most people will tell you that sanwa parts are better for fighting games so you should get the hrap ex and replace the stock buttons with sanwa but it’s all preference. if you’ve used a madcatz TE before it has sanwa parts so you know what to expect if you get the hrap ex and replace the buttons. they’re both good sticks, it just matters on your preference. however, if you do get a hrap ex you will most likely want to replace them eventually with sanwa or seimitsu sticks.
these threads have more info if you want to read more about them: