Sets/Raise or Slow Play

When you flop a set and get action, is it best to slow play a safe flop or just raise it up?

I think it depends on a few factors (meta game, table images, flop texture etc), but the basic problem is what I'm trying to get at. As an example hand, let's use a flopped set similar to one I played earlier today:

PokerStars No-Limit Hold'em, $0.50 BB (8 handed)

CO ($50)
Button ($50)
SB ($50)
BB ($50)
UTG ($50)
UTG+1 ($50)
MP1 ($50)
Hero ($50)

Preflop: Hero is MP2 with 6, 6.
UTG raises to $2, 2 folds, Hero calls $2, 4 folds.

Flop: ($4.75) 6, 5, 5 (2 players)
UTG bets $3.25, Hero ...

Assuming that villain is an unknown, or just an 'average' tag player, what's the ideal line?

If we raise, we obviously get the most value from the big pairs.
They might 3-bet us, or maybe just call and then call down the turn and river.

On the other hand, if we raise and he's got AK/AQ, we lose a lot of value. Villain isn't bad enough to call a flop raise with overcards, so we push out those hands.

Now assume we call.

In the situation when we're up against big pairs, it's going to be a lot harder for us to stack now.
For one, hands like JJ might think they're best on the flop vs a raise that might look like 88 or something, whereas if we call then raise or bet a K turn, we lose a lot of value since that card kills our action.
Another reason is that even if there is a brick on the turn (say an 8), we still look very suspicious raising at that point, killing more action.

Now on to the spots where we're up against AK/AQ, we gain a lot of value by slowplaying.
If we call, we might either get villain to double barrel, or if he hits an A or K he might think his hand is good at that point.
Even then though, he might not stack us since a flop call plus a turn raise doesn't fit much but a set (or maybe a bluff).

Metagame complicates things even further.
Taking a look at say, a flop raise for example. What other hands am I raising the flop with other than a set?
Basically, none.
In spots like that I'm usually just floating hands like 88.
So again, a raise is very scary, but hard to get away from.

Then again back to the flop call, turn raise.
I rarely if ever take that line with anything but a monster; ie I'm never calling that flop with 88 then raising the turn - there's just no sense in it.
He's either double barreling at that point or he's got a legitimate over pair, and I'm usually folding the turn with 88, so a flop slow play looks extremely scary to an over pair.

Player images have a pretty big impact as well, ie I might slow play vs a lag if I think he'll 3-barrel me, or I might raise an absolute nit who isn't betting the flop without an over pair.

Also flop textures is pretty straightforward in my opinion - if it's draw-heavy we're definitely playing it faster for obvious reasons, whereas on a dry board we might consider slow playing.

Anyways I'm ranting but I hope I made sense. Thoughts?