I am no authority on spark plugs, but here's my experience thus far...
Yep,
you can never go wrong with NGK Plugs. I'd like to try the Denso Iridium Power plug (like NGK Iridium IX only with a u-Groove on the tapered ground electrode and a 0.4mm center electrode) Just for the heck of it.
Champion plugs are good too (I've read that most of the indy car or F1 racers use them, standard equipment on most power lawn tools) , but it would be hard to beat the NGK, because they are #1 in spark plug advancements and quality in my opinion.
Be careful with some of the Autolite plugs (sometimes made by the lowest bidder in China), they have an outdated numbering system (not as detailed as NGK, Bosch or Champion), but they will work just fine on these engines.
I haven't tried the Standard Bosch plugs, but I have tried their Platinum +2 and +4 plugs on my car and they didn't work well with my ignition system(that doesn't mean that they wouldn't work well on other applications though).
Oh well...that's about all I know(not too terribly much LOL), but have fun out there and give every plug a fair shot or two and see what works best.