PvPvE is definitely the choice for me. The thing I dislike the most about Ilum PvP is that it has no purpose other than a giant zerg vs zerg fight to get some Valor. In order for that planet to be enjoyable again, it really needs to have some sort of fortress system, or something to that effect.
Also, having a city, fortress, or outpost somewhere in the game (not necessarily on Ilum) that attracts a high population, and has a large PvP area outside of one of it's gates (with a safe spawn area nearby) would be nice. The best open world PvP I have experienced in other MMO's has always taken place in areas that are easily accessible and that make new players want to try out PvP. When visiting Ilum, I find myself running into the exact same people who I regularly run into in Warzones. The new players that do visit the PvP area on Ilum don't seem to stay long since there's so much open space, and riding around looking for the action tends to do little more than get you killed. I personally went to the PvP area on Ilum shortly after reaching level 50 and didn't come back for over a month because I didn't see the point. The same can be said for the Outlaw's Den. It's a cool idea, but it's so far out of the way, and there is very little chance of new players stumbling upon it and witnessing a big PvP battle (and if they do, they will be auto-flagged and just die instantly anyway).
If open world PvP takes place in an area that is more accessible to players, and clearly visible to people who aren't regular PvPers (without forcing them to engage in the fight), it will attract more attention and be a lot more fun in the end. Watching some higher level players PvP at a city gate and thinking, "Cool! If I keep leveling up, I can get in on a fight like that someday!" is one of the things that originally got me really interested in MMO's.