If you've read the advantages and disadvantages it's up to you to decide where your priorities are. Urethane last's longer and provies a stiffer ride, but my experience is they occasionally need to be lubed to prevent squeeking (even the graphite impreginated ones) which is why I shy away from them on my own cars.

Stock bushinbg are cheaper, provide a smoother (softer) ride but deteriorate rapidly in hot dry climates or when exposed to oil (not a problem you should have where your at and if your building a semi show car)..