The new racer response...
Competeing in P1 in an old Justy, maybe I'm not one to talk, but I'm all for building your first... If you have the welding skills. I don't think you can really get an accurate picture here, because most people will be biased towards what they did.
As to the drivetrain choice, sometimes I wish we had started with a group2 capable car, but the Justy is really in a class of it's own, short, underpowered 4WD...
Pros for building (you building, not paying a shop)
1.It may not be significantly cheaper, but the cost will be spread out over a few pay cheques!
2.You can race an unfinished car quick, ie suspension not "finished" electrics not totally redone etc. put a cage in and go race.
3.You will know all the weak points in the car, and can be easy on it untill they are improved.
4.When it breaks, you'll know how to fix it, or at least be only blaming yourself (stupid rad at Defi!)
5.you'll learn a ton real quick.
6. you will probably have driven the car before changes begin, you can judge whether you like the car first.. and you can see what the changes do to transform it.
Tips...
Get to know your scrutineer before you take in the finished product, have them look it over during the build process. Things are easier to chage when they are only tack welded. and adding bars after the cage is painted is more work. (didn't have to, showed up with too many to begin with...)
make sure the whole shell is free of rust (silly Rusty Justy)
Strip the WHOLE interior the first time, and do paint it soon after.
Race it cautiously at first, to see what is wrong, and where
Things I wish I had done...
Given myself more time... more then a month, really tired at first race
Car with less rust... what would be insigificant on a street car, is a nightmare on a rally car.
Seam welded the strut towers and front sub frame during inital build, not after bending things... silly practice jumps!
Just build it