There's quite a long list of things ladies look for in a man when they are searching for their "Mr Perfect". Ambition, sense of humour, good looks, personality just mentioning a few.(I know many ladies beg to differ with their text book sized list) but one of the first things she would notice about a guy is his sense of style. If you have a sharp style and dress smart, you would have won a larger part of the battle and would have impressed her a great deal.
Dressing smart radiates that air of confidence the woman craves for from the man. There is nothing more attractive than a man who knows who he is, and being sharply dressed gives that impression.
With that sleek style, you ooze of sex appeal. I doubt there's anything that makes a lady weak to the knees than a good looking man dressed smartly in a well fitted suit and if it is her man, she'll be proud to show him off to all the other ladies probably having their eyes on him.
Being neat and smartly dressed sends a message to a woman that the guy may have some dignity and class about him. If he is careful in his personal appearance I think women may think he is dependable in other areas as well. It says "I take care of myself, I'm responsible & respect myself and will most definitely have respect for you." From personal experience, I have been complimented quite a lot of times by ladies because I have been sharply dressed so I know this for sure.
They say "clothes really do make the man" and If you can dress yourself, you will probably succeed in whatever you do (Even if it is getting the ladies). So guys depending on the occasion and place, it's quite sexy to turn up looking sharply dressed. Please don't go turn up at a beach party in a sharp suit and tie thinking you looking all dapper. You won't get the ladies, you will get the stupid look.