Folding Bikes - Q's about Dahon Mariner, Speed d7?

Comparing the specs on the Dahon site, the Mariner and d7 seem to have the exact same components, both made of steel, with fenders and a rack as accessories. The price difference is like $10 or so. The mariner does weigh about a pound less. The vitesse seems to be an aluminum version of the d7, otherwise, I see no difference. So, can anyone tell me if there is a difference between these 3 models?

Also, can Big Apple tires be fit on any of these models? I notice the Speed p8 has the big apples but no fenders. So I assume the big apples can fit on the lower-end bikes, if the fenders were taken off....
I compared a MTB with no suspension and underinflated tires to my MTB with suspension and high tire pressure. There wasn't a huge difference, though I never traveled over the worst roads. So I figure I could get a lower-end dahon with big apples over a front-suspension downtube. Reason is that the downtube is 30 lbs and aluminum compared with ~26 lbs on a Dahon with a steel frame, which I assume will be better for riding on rocky roads. The 4 lbs wont really matter when riding, as I carry 30 lbs of stuff, but I know it will make a difference when carrying the bike if needed.

I am planning on buying a Mariner over any of the other bikes based on it's lightest weight and steel frame, assuming the big apples can be fit on it. If not, I MIGHT spring for the Speed p8.....not really wanting to spend the extra $100+, don't tempt me though! What I WILL spring for is the extra cost of the 07 models for the adjustable handlebar height. I am 5' 5", and the fixed height one was a bit too high for me. Comments, suggestions, all welcome! thanks!

http://www.dahon.com/forum/index.php

A rule of thumb for any bike, especially the differences between Dahon models is this-the more you spend=the more better quaility components plus probably more accessories offered on that model. If you go cheaper, you might have to add a component/accessory later. That is fine if you are only adding, say a saddle or a bike light. But if you are doing a major conversion (like a complete drivetrain like I did on my Boardwalk S1) or adding many new components/accessories to the bike, it is probably better to get a higher up model. The last Dahon I purchased (last November), I chose a mid priced one with the drive train that I wanted, only adding a saddle. The purchase price stayed where I wanted it to be. Unlike the Boardwalk, where I had to build a wheel with the three speed hub, plus add a shifter, and a hand brake which doubled the original price.

Go for the model that closest fit your needs and climate (wet or dry) where you will ride it.

I love my Speed P8, so I am biased. Having said that, the price difference you are talking about ($100) will get partly eaten up by buying the Big Apples. The Speed is a great bike. It rides well, quite comfortable, stable and responsive. It also includes the pump in the seat post, and is light enough to carry.

FF is right though, you need to make sure the bike you buy has the major components that you want, or your costs will sky rocket.

Enjoy whatever bike you choose. There is no bad choice if you get out and ride.

the mariner look to have the same frame design and material as the boardwalk with different color.
i would not buy it as my boardwalk snapped in half with light usage.
the newer frame design on the speed may be stronger.