i've preferred leveling solo so long since i didn't feel like looking for parties and really needed the money from drops but today i partied with a cleric in moonlight tomb and everything was so much easier so i'm torn between getting drops to get money to save up for later extremely expensive things and leveling faster than i normally do D:
Well, you should have less downtime if you have a partner so you'll kill faster which helps even things out. You may only get half the drops, but there'll be more of them. I most often duo with a cleric as a fighter and between increased killing speed and money saved on hp stones it couldn't be better.
Do both? Not at the same time of course. xD Was the item pick-up sequential? If so, you still gain something. I personally don't look for parties except for quests, though I may sometimes join one if I'm bored. o-o But for me i guess it doesn't matter as I run out of inventory space really fast anyway.
I'm pretty sure the higher up you get, the more important partying is. You most likely won't want to solo the harder areas, but I don't really know. Moonlight Tomb is bout the hardest area I've been to so far.
Soloing at higher levels is really boring. x__X It's like.. you grind grind grind, then look at your exp bar, and it would look like it hasn't moved much. Dx
But when you're partying, you get to chat with your party members.. and I guess time passes faster and it's just not as boring to level. xD