Telly,
All 3 of the units you mentioned are quality products. Properly installed, they will all serve you well for a long time. The difference may have to do with the source. The big box stores are not well known for quality, worry free installation. It's not their strong suit. I'm guessing if you got installed pricing from local lumberyards or contractors familiar with Pella and Andersen, the installed prices would be closer to the Marvin price. But big box vs certified installer is not an apples to apples comparison.
If I were you, I'd get at least 2 prices for each unit. Then compare them all, and decide which options/features are most important to you.
That should help narrow down your search.
Good luck.

Hi Telly,
We did this research in '03 and it took 5 months to research various brands. You may want to also look into Loewen, a brand that we just saw recently at a friend's new house. They seem to do really good work.

We had to decide on quality as well as looks. At the time, vinyl, fiberglass and other composite looked weird even when colored. The neatest look was Aluminum so we settled for Aluminum cladding and wood interior. Things may have changes since then.

We compared extruded Aluminum versus rolled aluminum, how do they bake on the color and what type of protection do they use, how the cladding is mated to the wood interior, whether the wood is solid wood or veneer, locking mechanism, ability to adjust height and extension of operating units, quality of interior wood work, glass and wood options. Finally, we needed to know if they could do what we needed for our somwhat odd-ball opening.

Pella offers Duracast and something called Impervia, some sort of composite material supposedly stronger than Aluminum. You have to go see in person how they look and whether they meet your requirements.

Andersen also offers some sort of special glass coating and some kind of exterior cladding other than Aluminum. You need to see them and decide whether they work for you.

If you decide to stain the wood, it will be important to look carefully at the wood work to see if the lines are appealing. Different companies have slightly different way of finishing the interior. If you intend to paint them, then that may not be so important.

If you see a window showing poorly in one store, find the same window in another store. We saw an Andersen in one shop being shown with visible gaps in the woodwork and even frayed ends. We went to another shop and the demo window showed real well. The local Home Depot and Lowe's were just not good at all in showing Pella windows and doors. We had to go to a shop in another town.

Nothing beats close-up touching and looking at the windows and doors in a good shop.

We settled on Marvin becaus we prefer the Marvin woodwork quality but that is just our taste.

Good luck.

Mike35 and calbay03....thank you both for your replies. They've given me a direction to focus my energies!
Telly

In my experience, I would NOT recommend Pella. I've had many issues, such as seal failure and cladding problems (among other problems), with my Pella Architect Series windows and doors installed throughout my home 1995. Please check out this website, detailing the various window and door failures/defects: www.onlinelitigationdiscovery.com Also feel free to share any similar experiences on my website.