I think you answered your own question - it terms of having to lose weight is a few oz. even an issue? All bike magazines will tell you to physically (ie off you) lose weight and not compromise the bike.

In term of bikes, you need to determine your riding style and what appeals to you most. My new bike is extremely twitchy compared to my old bike and at first I hated it but now... I am in love! My bike "jumps" off the pavement when I want to take off. Of course a twitchy bike has other issues.

I do think larger riders tend to have different profiles... larger generally means you are stronger on flats and can move with power... you need a bike that accomodates that power. A lighter rider never really has to worry about flex.

Another thing to cnsider - your age... your are probably young and so this may not be a problem but if you are getting up there, remember that more agressive positiing may be difficult to maintain. My old bike was agressive. My new bike is less and I dont regret the change. Of course i am 60 and don't bend like I use to. I want to keep riding this bike at least another 10 years so I had to factor that in...