I've only played Disgaea. Is it better than Disgaea 5? Trying to figure out what srpg to get.
It's different than Disgaea. 'Better' is subjective to your interests.
Disgaea is all about endless upgrading - the game understands 'grinding' and is built around the concept, making grinding fun and making it the 'game' itself. Heck, even items in your inventory have procedural generated 'dungeons' you can enter to level the items. While there is a story, it's relatively easy and the real deep game is elsewhere. Combat is relatively similar at first glance, although Disgaea's color blocks really turn every stage into a puzzle [you can sometimes defeat stages with a single move].
GW has more of a FFTactics structure. That is, it's story based with a series of battles you need to face, with the ability to revisit old [slightly different] scenarios if you need money or exp. While it's still about character progression [all srpgs are, really], it's got a completely different mechanic, the job system [primary, secondary, unique]. So you can make a character a monk [main] warrior [sub], and he's got his own unique skills as well.
Ultimately, Disgaea is sort of like math heaven. Both in min/maxing characters and items, but also in solving dungeon color block puzzles, etc. GW is more of a straightforward adventure with srpg combat, where you still guide character development over the course of the game.
They're definitely different, though definitely in the same genre... but it's hard to say one is definitively 'better' than the other. In general, I like Disgaea more than most SRPGs because the difficulty progression is -made- for grinding, and as such, there is always a challenge there if you want it, where FFT style games allow you to easily grind yourself into gods. However, I do like the 'feel' of GW more than Disgaea.