pumpkineater,
The biggest mistake people make is that they believe clad windows are "no maintenence" windows. That's simply not true. There is no real "no maintenence" units, only "low maintenence.
If windows are ignored for a long period of time, they can develop problems. That's true for any type of window, whether aluminum clad, vinyl clad, painted, hollow vinyl, etc. Once a year or so, the units should be looked at. Especially around the top corners, perimeter, and sill. These are the areas where water is most likely to find a way in. While the cladding/color can look fine, if water has a gap, even a tiny one, it can rot the wood under the cladding, or rot the framing in the wall.
Every unit should be inspected yearly, and cleaned/caulked if needed. This will insure a long life.
The other thing to be sure is a good quality installation from a knowledgable contractor. This can make a huge difference in the windows performance and longevity.
Good luck with your project.

Pumpkineater:

What Mike says is true, there are no maintenance free windows. Having said that, if you are going with wood windows the metal clad ones are the better choice. Another important issue is what size the windows will be. Some manufacturers do not upsize the window frames for larger sizes and the windows do not function correctly due to warpage without constant adjustment. Loewen windows are notorious for this problem. Whatever you get, make sure that the larger windows have upsized frames.

Mike's advice is right on the money. PNW's advice is confusing indeed. I've never heard of different sizes having different thickness frames. It would be odd to have a 30" x 50" window have a 3/4" thick frame, and a 30" x 60" have a 13/16" frame, and a 30" x 70" have a 7/8" frame, etc. NOBODY does that. I would challenge the statement "Whatever you get, make sure the larger windows have upsized frames." How do you check for that? When is it necessary? When is it not necessary? Where does one draw the line? Perhaps what he meant is that when a window exceeds a certain square footage of glass (which he didn't specify) the window needs to have perhaps a thicker glass, different weatherstrip, and different type of frame. If that is the case, one could simply state "Make sure that your windows have a DP rating of at least ___." The DP rating requirements indicate how structurally sound and water-resistent the window is, and the DP requirements can vary with the conditions of your home and environment. Or, perhaps he meant that if you get really large groupings of windows (e.g. 10 windows mulled together), that they be designed to resist deflection and water infiltration by having reinforcement mulls and/or special flashing. Some window companies do a better job of that than others.

Since you live in a heavy rain but moderate climate, getting the highest R value isn't really a primary concern. Of the three brands you mentioned Pella generally has the best performance. When Consumers Report Magazine last tested windows (3 years ago?), they tested for air and water infiltration and Pella was their recommended window, but they tested double hungs. I don't know if you're getting casements or double hungs or something else, but all three brands you mentioned are nationally known.

Pumpkineater.
The 250 series is Pellas Proline series. While I don't know about the testing habits of the Lincoln and Jeldwen brands, I do know that 100% of all Proline windows are tested for water and air infiltration at Pellas factory. The other Series that Pella offers have random testing. However, during the random testing if something is found with a test flaw, all products in that line are pulled and re-tested going back the the previous random test.

Thanks for all the advices. Our prefered choice is to get casements. Due to budget reasons we most likely will mix in some double-hung windows to lower the cost.

I agree that wood-clad windows are not maintenance free. But how do you seal the mitered aluminum corners? It would be very difficult to get any caulking in there?

Since the first posting, we are now also considering Timeline windows. They are vinyl windows made by Lincoln.

TRU-BLUE your comments are right on..this "PNWARCHITECT" has it in for Loewen and never makes sence, and does not respond to my challenges to prove him wrong...I believe he has logged in under other names and made similar statments about Loewen...might be fired employee...not sure..

PNWARCHITECT...you are a bit rediculous...you make these unfounded claims about Loewen in about every topic you see that has the word "window" in it. Why don't you tell me what happened on your project for real in an email to me. YOU DOn't KNOW WHAT YOU ARE TALKING ABOUT WHEN YOU MENTION LOEWEN FRAME THICKNESS. Loewen's frames are thicker than any other product on the market, unless you are talking about a custom mill or Tradewoods or Heartwood...my email...sbutler28@hotmail.com...We do not change our frame thickness for larger units, they are the same for different sizes, and thicker than other companies