I have tried both Monocote and Ultracote and hands down prefer Ultracote (Called Oracover here in Europe).
It's not a big deal to put layer on layer but requires initially low heat to tack it down without bubbles.
Also the paper backing is great to draw patterns on before cutting, paper backing comes off easier than the Monocote plastic backing.

Overall I belive Ultracote is more user friendly but for a more experienced builder it might make less of a diffrence.
Go Ultracote for your first cover job. Get good tools such as covering iron and heat gun... Also stock up on razor blades and #11 blades, you NEED to have sharp blades to trim the material.

A tip for covering in tight corners without having any special trim iron or tools:
Put something out of metal on your normal covering iron, such as a normal kitchen spoon or handle from a fork.
When it's heated you use it to tack covering in hard to reach corners.
Of course you need a glove since the whole thing will be hot.