Automating casement windows?

what is the best caulk to use when istalling windows? someone said OSI QUAD. is that only for exterior or could that same OSI QUAD be used for interior as well? is see some of these marketed as silicon and some as just caulk, is it the same thing? thank you guys

I've got to quickly ready my fixer-upper for resale, so I'm suddenly switching to general contractor mode to do a lot of the things that I've been meaning to get done. Among these tasks is replacing the windows. This morning, I recieved an estimate from one company, who offered a price for their self-manufactured windows with argon and a product they sell from another manufacturer, without. I'm also expecting another estimate this evening or in the morning from another fellow, who buys windows off-the-rack and I'm pretty sure, based on our conversation, his doesn't include argon. The bid that I have on-hand is about $1500 less for the windows without argon. There's also a difference in frame-width, so the argon isn't the only difference, but the salesman says that his windows have an R-value of 3.3 and the other company is around 2.8 and the literature says the argon-free has a U of .34 and an SHGC of .35, while the argon is .30 and .21, respectively. My instinct is that because I'm not going to be living in the house, I probably should go with the lowest bid (from a reputable company), but I've never bought a house with dual-paned windows or argon gas. Does anyone have any opinions or experience about whether, if I were to go for the argon, it'd have any effect on the eventual purchase price or the appraised value of the property? As I told my wife on another subject, I feel that anyone looking to buy the place will offer down in $5k or $10k increments, so the $1500 might not result in a bid-down, but if it resulted in a higher appraised value and a different starting price, then that might be another matter, altogether. Thanks in Advance