layz has some excellent points above.
I've only flown Vueling and Easyjet. Vueling didn't feel any different to being in Economy class with a regular carrier. Overall a positive experience. The fact that their FAs were (more often than not) gorgeous didn't hurt either. Easyjet definitely felt like an LCC, but that was mainly due to the open seating policy. I likely wouldn't bother with Easyjet again since after all the add-ons, you can often find a seat on a regular carrier for around the same price.