not saying this is gospel but for me the suited connectors offer an advantage in that while they can hit a straight (just as the unsuited connectors can) they also have the possibility of a flush or even a straight flush. it's these extra outs / possibilities that cause me to value suited connectors higher than unsuited cards.

you make a good point in that there may be someone else out there with higher suited hole cards - this can be minimized by playing the higher connectors ie: 6 or 7 and above, reading the board (if you have 89h and the board is AT3h then the number of cards that can beat you has been reduced) and the players - it's usually clear what people are betting - it's not going to matter what value cards you have if your opponent is betting TPTK and has no cards of the flush suit in his hand. I know these are oversimplifications and yes you have to be much more careful playing a low flush but in the right circumstances it will pay off.

hope that makes some sense...