As a pilot LGW is going to be more challenging and will give you a lot of exposure to different destinations and interesting airports.
Very impersonal base though, with 70+ planes based.
If what you are looking for is quality of life, good weather, food and fun things to do, even with less money at the end of the month (debatable, SOs and FOs don’t have great conditions in either base), Barcelona is probably a bit more enjoyable than Crawley (or London, but that’s personal I guess), and that’s an understatement.