Just my .02
27 is a waste b/c there are only 6 channles and there is a 1 in 5 chance of having some one else with the same as yours.
75 is the way to go b/c there is a 1 in 30 chance of having a similar channel and you can get a excellent radio for around $100 or less if you shop around.
Spektrum is newer technology, you will never have to worry about channles but it is very expensive and un necessary.
So many people are buying Spektrum that it is leaving more of the FM channels free and increasing your odds that you will not have the same frequency as someone else.
My vote is for a good 75 for around $100