I'm no expert but do use both MAS and West Systems.  You shouldn't have any problems.  I prefer MAS because I think West Systems goes off quicker, giving me less time to work, but the end result should be the same.  I'm sure other, more experienced folk, will jump in.

Thanks for your input Jack

 Dan 

I have also used both.  West can go off quicker, but that depends on the speed of the hardener.  The fast hardener (and possibly other speeds as they age) is dark and not suitable for any application that will be finished bright.  I had some leftover West epoxy and used it for end pours.

You may get amin blush with West System.  Not sure if that can be avoided with slow hardener.

Paul G.

This is probably a 'no brainer', but do not use the West resin with the MAS hardener as they are not formulated to work together.  If you mean that you have done most of you build with MAS, and want to use West Resin and West Hardener in a different area, or over FULLY cured MAS, then this should be fine.  - Ron

I've used only West, and can tell you that stilljustseven is right. The fast (or low temperature) West hardener will impart an amber cast even if it's fresh, and as the hardeners age they will darken. This is especially true if the can has been opened and partially used. This darkening is most severe with the fast hardener, but it also happens with the slow (or higher temperature) hardener as well, even though the fast will be nice and clear if it's fresh.

I suspect the rate at which the hardeners darken is related to humiidty, but wouldn't swear to that.  By the way, this darkening process occurs slowly, over a period of weeks if not months. If you used part of a can last weekend and it was fine, you'll have no problem next weekend.

In case you're concerned, the darkening of the hardener doesn't seem to have any structural effect, at least not in terms of what we're building.

The amine blush shouldn't be a problem; all it seems you have to do is wash it off with clean water. Leastwise, that's all I've done, and it's never been a problem later on.

Having never used MAS, I can't compare the two brands. 

 Ron Paro is right.   Do not mix hardener from one brand with resin from another.

The West will blush.  I really enjoyed working with it and was disappointed when I learned that my Chess 16 kit was coming with MAS.  After working with it for a few weeks, I like the MAS better.  Odor is more like ammonia with MAS vs chemical with West.  MAS claims  to not blush.  Blush is no joking matter.  I had paint just peel off of a West covered small boat that I had thought I had adequately sanded and washed.  It might have been something else, but I think it was blush.  If MAS (with slow hardener) truly does not blush, I would use nothing else to wet out fiberglass.

The West system is not supposed to blush, you should use the 107 west hardener for clear coating which i believe to be the clearest on the market check out the West system website its all there.