A trick I learned from my dad as a kid was to stick to one color scheme (I use Red White and Blue) This way, any "Leftovers" can be used next time and you don't wind up with a box of mismatched colors. (Of course, you still may need the occasional Yellow for a cub, etc. but it really keeps the odd colors from piling up)

Ok, here's the scoop on MK vs UC:

If you know anything about painting, this is a good analogy - MK is like Lacquer and UC is like Enamel. Lacquer will give you a nicer finish, but it's a lot more critical in its application whereas you can just slap enamel on and it will look good.

Next, MK's adhesive is more permanent. Once it's on, it's hard to get off and the longer it's on the more difficult it becomes to get off whereas UC can be easily heated and removed.

Also, UC shrinks and stretches a LOT more, so wrinkles are much easier to remove.

Now, here's the tricky part of using MK... We all know that they both shrink, BUT, as you learned back in 6th grade science class, when you heat something, it EXPANDS. This is also true of covering. As you heat covering it starts to expand, then, once it reaches a certain temp, it begins to shrink.

So this creates a problem - Due to the expansion, unless you are EXTREMELY careful, you're going to get a wrinkle somwhere.

Now, here's the rub - If you iron down a wrinkle with MK, it is there for good, but if you iron down a wrinkle with UC, just keep applying heat and it will pull out.

This is due to two factors: First, unlike MK, UC's adhesive will release from itself (once MK's adhesive sticks to itself, it takes an ape with an air-hammer to get it unstuck) Combine that with the fact that UC shrinks so much, the wrinkle comes out easily.

I also find that UC is not as brittle as MK. When it's cold, just a slight bump can split MK. UD tends to dent rather than break and a little heat will pull the dent right out.