Kazuma the best when it comes to track/off-road use since it's illegal (straight pipe and very loud)
but other wise the TRD
is the best for gains and some would say sound.. end of story.
If you want a good gain and that's it well there is a thread on here for DC header which is suppose to be cheaper than the TRD
exhaust and either a slight amount more or the same hp gain.. my only thought is it probably balances out with costs of installation if you cannot do it yourself.