Jeld-Wen are also easy, 2nd most expensive
Anderson are easy to install and the least expensive of the three. If you live in termite country make sure that the wood has been treated or go with an aluminum frame.
I had Pella's in my kitchen (that were not treated ) and the termites ate them up.... 5 windows at 890.00 a pop....
The Marvins we used were bombproof. They use a cool metal tounge that you secure on the inside of the rough opening, and these units came with the brickmold on
Pella has lots of instalation guidelines, omitting or altering them can void the warranty.
They are both great, cost was not too much different. Custom and odd orders in our style would have made the Marvins more expensive, but there are a ton of variables.
When I replace the windows on MY home, I'll be going with Pella. I happen to like the integral blinds and found removing the componants not too bad, but I'm not a painter and don't have to repeatedly do this.
find one that you like the looks of. Find a certified installer/contractor and make sure they do a good job.