It really depends on personal opinion, and the perfomance and longevity you expect out of your plugs.

Denso:
Some tuning mags and dynoed with Denso and claim up to a 15hp increase at the wheels. 15 hp was a RX7, so it's a rotary engine, but a starndard engine can expect a mild HP increase. They burn better and don't often suffer spark retardation, etc.

If you don't know much about your car, throw in OEM...they'll work fine, and replace them when you need...if you're turning your turbo or doing some performance mods on the engine, you might want to consider other routes....colder plugs, etc. If you are dearly attached to Bosch you can get different temp plugs from them too, of course.
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Brandon
95 854T 92k
Pictures =)