$1000 now is a whole lot cheaper than the medical bills later in life when you come down with diabetes or any number of other things. It's also cheaper than smoking, drinking, or a lot of other things that have very negative effects on one's health. Or you could go with the "well it's either this or I'm buying a ferarri." line.

Me, I started off cheap, showed my wife I had a real interest and desire, and she hasn't said much about my cycling purchases since. My folks on the other hand, still have sticker shock when I mention how much I spend on this or that. So I stopped telling them.

As far as differences between the models, if it's mostly 105, then it should be good for you starting out. Anything above is a decent amount of overkill for a first bike especially if the wife is having sticker shock already. One thing to look at though is the wheelset included on the two. Not sure which the two are equipped with, but that's likely where at least some of the difference in price is coming from.

Btw, it's tax time, if you have anything coming back from ole Uncle Sam, try to arrange it to use at least some of that money to go towards the bike purchase. I live near RBM on coit, if you want a slightly more experienced aid that's not there trying to sell you a bike, I'll be happy to try to make it over there next time you go to look.