i reckon there is nothing wrong with going either way copper, iridium or platinum.
each has it's own advantage and disadvantage.
if you are paying someone to replace coppers every 10,000km then they will prove to be quite expensive. as a DIY (allowing you value your time at $0) then coppers are possibly the best bet.
i personally doubt iridiums will actually last 150,000km AND perform at their best if you have increased the performance of your car. if you are going to check them every few years you might as well replace them at that point. i remember reading (i have no source handy, sorry) the performance is fine for at least 40,000km.
so generally i run iridiums for a couple of years and swap them out. it works out fine on the cost front and they perform identically on the street to coppers. i have used some coppers on the stagea back to back with a set of iridiums and there is nothing to separate them (using the ol' seat of the bum dyno).
my R33 was back to backed at UAS and the iridiums showed an extra 1-2kw back to back (should be on their website somewhere) but this is probably just variation in time/temp/old worn copper plugs.