this question can only be answer base on the hp level. at higher hp the civic are cheaper build and more competitive. i am talking about 500hp+ here.
here is the advantage and disadvantage break down of a 500hp+ car comparison.
-colt need shep tranny=1000-3000 for colt and civic gsr tranny=600-1100
-rods and pistons= about same but slightly cheaper for the civic
-injectors, fuel pump, intercooler, exhaust are the same price but slight advantage to the civic due to many manufacturer
-colt need 4g63t=free to 1500 and civic need b18=free to 1700
-colt really need cams=350 and civic does not need cams due to vtec=0
-colt does not need sleeve=0 and civic need sleeve=1000
-colt need coil over to clear slick=100-300 and civic need axle=300-1000
-colt chassis=200-500 and civic hassis=500-1500
-colt need dsmlink=600 and civic need chrome=150/hondata s200=300
-civic need msd ignition upgrade=350 and dsm does not=0
-colt need valve spring and retainer to turn 8000rpm and civic does not
-ported 4g63t head can cost 1500-3000 but can will not out flow a stock b18c/b16a2 head
there are not much advantage that a colt have over the civic. it cost money to go fast with either car. wehn you get into the 600hp+, the civic gain advantage because you don't have to sport a $6000 dog box tranny or a full $3000.00 race shep/tre tranny. b18c are very efficient and it will make more hp than a 4g63t due the the super efficient head at the same amount of boost. 4g63t will make more torque but once you switch to the short runner intake, they make very close to the same. civic are lighter than a colt. stock grs tranny is so good, it makes shep tranny fells like it is grinding. b18c head can rev to 10k with out a problem. 4g63t heads will run into a problem with breaking the rocker arms and having them jump off at that rpm.
for a few dollar more i would build a civic. for guys on a budget, colt rules.
wow!! i have a friend with a built b16 with $7000k in the motor. i took a stock long block($400) and put down $347whp with $1200 in upgrades. while he made 352whp, so on average cases the 4g63 is cheaper to build. as far as civics being lighter than colts show me that, because i don't believe the hype. i'll rather have a 4g63 powered csm than a civic