Both hands can be overplayed...for that matter it's possible to overplay any hand. Because no-limit and limit are two completely different games your question needs to be answered twice.
NL: There's no question that AK suited or not is a great hand preflop. It's better in a tournament than in a cash game because if the blinds are high enough (late in a tourney) it's worth taking a chance at a coin-flip to win them. When the blinds aren't large, as in a cash game, AK needs to be played carefully. It's a big raising hand, but not a big-raise calling hand...if you get my drift. You have to be able to dump it if you don't hit the flop; if you fall in love with it you'll go broke.
Suited connectors are good raising hands (especially in late position) because you may win the pot immediately, and if not, you know whether you've improved on the flop. If you haven't then you dump it and lose no more. They are also good hands because you can win a big pot if you do flush or straighten if your opponents are likely to go to a showdown holding top pair, etc. You can limp with them as well but if you do you give up the folding equity you gain when you raise.
Limit: AK is a great hand but it can't stand to play in a multi-way pot, so raising (and re-raising) is essential. You have to limit the field so that your top pair hand can win. You mush get rid of the players who are holding drawing hands. As in NL, don't get married if you whiff the flop and can see that your opponents have hit.
Suited connectors are great limping hands in limit. You hope everybody plays, builds a huge pot, and you get to collect when your flush or straight hits. Is 67s going to be able to win? When the 3rd flush card drops and you bet, if you get raised your chances aren't great; check/call your way to showdown. If you get called don't stop betting; your opponent can have the lone ace of the suit and be hoping to catch the 4th flush card. Don't let him draw for free.
In limit, you often have the right odds to chase, so don't be worried about it. It's the right play even though you're an underdog to hit. In no-limit you almost never have the odds you need unless your opponents underbet the pot. That doesn't happen often, so normally you only play a hand that can build a draw from late position...it limits your exposure.
Normally, I am more happy when a straight draw appears than I am when the flush draw does (even though my connectors are suited). Everybody can see the flush when the 3rd one hits, but straights are often hard to recognize.