This article is from the Radio Control (R/C) Flying FAQ, by Shamim Mohamed firstname.lastname@example.org with numerous contributions by others.
Depends on your preferences. I prefer gliders; that's where I started. The
2m (6 foot wingspan) class is a good size---large enough to be easy to fly
but small enough for easy transport. Beginner gliders are lighter, fly
slower and are more acceptable to the non-flying community than powered
planes---no noise or mess. Gliders are also cheaper (at least the trainers
are) than powered planes---no fuel, batteries, starter etc. to worry
about. Electric Flight is silent and clean so finds greater acceptance
from neighbours etc. at the flying field, although some people feel that
electrics are not robust/easy enough for beginners. There is a little more
paraphernalia - you may need spare battery packs, but you can fly from
smaller fields. Power (with engines that use a fuel) will let you fly
longer, and your model doesn't need to be as light as with electric (so
it's likely to be easier to build); however, you may have to go to a field
far from populated areas.
Whatever you pick, stay away from those sleek fast scale jobs! They
look nice and fly hard, and those are the last things you want in your
first plane. Stick to the trainers - they might not look as glamourous,
but they will make you a much better pilot.
And the most important point - no matter what else, try to find an
instructor! This is the one thing that may make the difference between a
rewarding experience and endless frustration. R/C pilots are friendly, and
most will gladly teach you for free.