Well, I've never hacked, but from what I know, RMXP is easier to use.
You just miss out on a few things such as some animations (title screen, attacks), contests, and obviously the ability to play on a GBA flashcart. However, you get a lot more freedom, and a few neat features impossible with hacks such as character shadows, a particle engine, and a few new minigames. Animations can be done (they just take ages), and with decent scripting knowledge, basically anything else can be reproduced.
Anyway, why I think game making is easier. You don't have to do sprite/tileset/OW indexing, inserting etc - you can just save the sprite in the appropriate folder. It's easy to edit Pokémon, moves etc by editing text files. Mapping and eventing (or what hackers usually call scripting) is much easier - you get 3 layers to map with, and you don't have to learn any scripting commands. The event editor is integrated into RMXP anyway, and includes important commands such as text, movement, switches/variables and conditionals, while others such as the shop or adding Pokémon are a single line of scripting (e.g. pbAddPokemon(PBSpecies::PIKACHU,10) would add a level 10 Pikachu to your party).
As I've already said, I've never hacked, but I'd be surprised if it was easier...
Just keep in mind that RMXP (the only game maker with a complete Pokémon starter kit) costs $60. You do get a 30 day trial for free, though, which is enough time to decide whether you want to continue using it or not.
