you should probably check out some reviews and gameplay videos before. or if you have access, at least give one of the other EO games a spin first, just to see if you like it at all.
thing is, while EO has great customizations for your party, its also full of repetition, lacks character depth and story, and you can also screw your characters pretty easily, simply because you have every option to screw them up.
now, i haven't actually played the 4th game, but since they didnt change things in the first 3 games, i guess these things are still the way they were.
you'll have to use some kind of guide to make a party that wont force you to grind even more than you would have to with an actually thought out and strategically good party.
monster hunter on the other hand, while looking cool and being a great hit over in japan where you just have to throw a stone to find anyone who'd go and play multiplayer with you, has its downsides too.
its a slow game. its more of a strategic game, than an action game in my eyes. you'll spend hours collecting items by beating the same things over and over, selling items or build traps, roasting food, getting all the potions and armors you need to stand a chance against all those cool monsters. combat, if it didnt change all too much from wiis monster hunter tri, is kinda weird. i cant put my finger on it, but it just feels unnatural. theres a rather limited amount of maps too, you'll be revisiting the same places over and over and over. you'll be doing tons of micromanagement, meaning you'll spend lots of time just to search for the right items in your inventory and the item chest, so you can carry them to a smith or to whoever wants something from you.
both of these games are extremely acquired tastes. and you shouldn't just blindly buy either one of them.
so my advice would be, for EO, to aquire one of the first three games and play them for lets say an hour. see if you're into it at all.
and for MH, go on youtube, look for a nice video (look for some random lets play footage so you see what happens between all the cool giant monsters), and see if you even want to try this game afterwards.