At a 9 player table, straddling in UTG is a losing proposition if you are only considering the money you are putting into the pot vs. the
odds of winning the pot blind. That being said, the side-effects of straddling can more than make up for that.
If you're a tight player and you want to hide that fact then you should straddle because a person who is straddling every hand gives off a strong impression that they are just here to gamble and not play real poker. It makes you appear looser than you really are which, if you're good, you can capitalize on that when you have a good hand and no one believes you do because they think you're loose because you straddle.
A second benefit of straddling is that it annoys or even angers the BB and SB who end up losing their blinds or putting in double when they normally wouldn't have to. This is beneficial to you because any time you can annoy someone you can throw them off their game. Plus, with them being to your right, you're already at an advantage over them. So easing them into tilt is only giving yourself that much more of an advantage over 25% of your opponents which is a high percentage.
Playing shorthanded however (3 or 4 players), straddling is a MASSIVE advantage. Look at 3 players. After the flop you're the button so you go last. Normally, preflop you go would go first. but if you straddle, you get to go last the entire hand. Plus, in a 3 handed game the odds of your opponents catching a hand that is playable against 2BBs is far less than at a full table, meaning you can get a lot more folds to your straddle.
I guess to sum it up, if you want to piss people off and make people think you play loose then you should straddle in a full table. But if you're playing very shorthanded then you should always straddle.