I have both a 26 and 19 as well as a P3AT for pocket carry.
I carry the 26 more than the 19. Although since I have switched to AIWB the 19 gets more carry time now. It's actually pretty easy to conceal up front.
I went down the exact same road as you. Bought the 26 first. Bought the 19 because, well, if you like Glocks you kinda have to have one. And then the .380 for pocket carry. I never carry the .380. The more I read, the more I wanted to be sure to have a more potent caliber if the time came to use it and I found I just wasn't comfortable with the .380. In no way am I trying to start a caliber war here...just sharing my personal experience/opinion.
I will be selling the P3AT to fund either a 442/642 or 9 Shield. More than likely the Shield. With a good, tuckable, AIWB holster I'll be able to conceal that just as well as the micro-gun in my pocket in addition to having a more powerful caliber.
As far as the trade goes. If you can only have one gun for now, I'd stick with the 26 as it will be easier to conceal. However, the trade is definitely in your favor dollar-wise. Heck, the 10 mags alone are better than half the value of your 26.