FWIW, I play 6-max almost exclusively these days, but I think what follows still applies.
I think it depends on the players that have limped. Are all the limpers loose passives that will call down and pay off your monsters? Are they all TAG and will put a lot of pressure on you when you hit TPGK or an overpair and lead out on the flop?
With a TAG table in which I think I can get some of the limpers to fold and to isolate, I usually raise in this spot. This gives me more information about what kinds and ranges of hands I will be up against, which is especially important being OOP and against stronger opponents. By raising, you can also represent a bigger hand than what you have -- it could be a monster like KK-AA-AK because they would be played the same as your marginal hand in this spot.
With a loose passive table with people that will call down every street with middle pair or gutshot draw, or if there are players that will get their stacks in with top pair any kicker, I'm probably completing with no raise to see a flop and hoping to get paid off by one of these stations. Raising is unlikely to get anyone off their hands preflop, and your marginal holdings won't often hold up against 4-5 limping stations. On the rare instances when you DO flop a monster, the limping stations WILL pay you off postflop regardless of how big the pot is preflop, so IMO limping is better in this situation.
Your own table image will also tie into this, since you will likely get many more callers if you are perceived to be pretty loose. The above is written with a fairly TAG image for hero in mind.