You HAVE to buy an engine, why BUY anything else?
MANWIN all the way. The rest are just expensive toys.
Manwin is extremely durable.
Manwin takes the least time to make.
Manwin doesn't break, the motor might, but not the Manwin
Manwin may be personallized with magic marker, paint, tape, anything.
Go to the Balsa beavers site and download the plans.
Download this plan for a stooge, 
With this stooge you just pull the running airplane out with the handle and it launches, just like the wing trapping Combat stooges.
Go to the Gas station, QT or convenience store and ask them when they will change their plastic signs next. They throw the old ones away, this is 4 mil Coroplast and is free for the taking, just show up on the right day.
Make ONE template, everyone can trace and cut their own with a sharp utility knife on 'Game Day'
If you can find the aluminum to make the motor mounts out of for free, do so. Otherwise, I purchased a piece at Lowes for 4 or 5 bucks that is long enough for 2 or 3 sets, then my flying buddy made a dozen or so sets out of scrap from work.
You have to have 1/2A control setups, you can buy these bulk from MBS supply or other place.
Make or buy half a control handles. Mogren of Pro Tech suggests making from plywood handles that have a 6 inch overhang. This vastly reduces control throw for the beginner. It also makes a dandy place to wrap up the control lines for storage.
Buy 14 pound test Spyderwire Fusion Fishing line, 150 yards for 4 or 5 bucks, you now have plenty of line sets. tie it through your handles and tie it on the belcranks, then adjust center through the hnadle like other half a handles do.
I'd buy Norvel Big Mig startups before I'd ever consider going to Cox engines. But if you have a bunch of those Cox suckers laying around, by all means use em if you can get em to work right. Make the engine mount aluminum longer so that the motor hangs an inch off the front of the wing. You should also make an aluminum backing plate to tie the two engine mount plates together, this will keep you from ripping the mounting lugs off yor Cox engines.
All the other airplanes are probably good flying planes, but screw that. The Manwin flys as good and will only be exceeded by a true 1/2A stunter and you can't hurt them. I've got a couple hours on mine, my flying buddy has a rediculous amount of hours on his, he actually is a little more fanatical about flying his. I flew Balloon Bust at Midwest Slope Challenge during the low wind day and put 6 or 7 folks up on mine, folks that haven't gone around the circle in years. They all had a good time flying and running it into the ground. No failures, just fuel useage.
From somewhere near Parkville, Mo.
William Crane
AMA 6733