Honestly, it's like apples to oranges.
They are completely different beasties.
The OLD (1998-2004 WC-1) Whizzers have a bad top end, the new ones (2005- current NE-5) have been re-designed and in stock for do very well.
Don't use mine as any example, as we HEAVILY modified it; I didn't prove it out, and make all the minor adjustments before attempting to ride it across the country. I'm still adjusting, but I am up to 45 MPH on it now, and more to come as I get everything tuned properly...
Anyway, back to your question-
Any two stroke will get more power per stroke over a four stroke. That's just due to design and the way they work.
The whizzer is a heavier engine, but is 148cc, it cost's more (the engine kit is around $699.00), as compared to the much lighter, and cheaper (I haven't priced the 80's lately, but my last one a few years ago was around 300), yeah there's the maintenance and repair, but well, honestly this hobby is a tinkerer's hobby- of all the bikes, my rack mount systems required the least amount of maintenance and repair, but the bike itself was always in need of P.M. (preventative Maintenance) just by virtue of the vibration and pounding of putting an engine on a bicycle, this is going to be neccesary.
Um, the Whizzer (NE-5) needs only to have the intake plate bore opened up to match the carb and port size, and the muffler baffle modified. Most people only remove the fiberglass packing from around the baffle and call it good.
My little 80cc two cycle, I've only improved the intake/exhaust gaskets, and get up to around 28-30 M.P.H.
Again it all depends on your intentions, what you'd like to use it for and all that, and really for a low maintenance machine, perhaps a GEBE kit is something to consider. I have no experience with them, but there are many members here who love 'em.
I myself have many different combinations for different purposes, including my 100 cc honda motorbike 1/2 size chopper which I use for commuting, running errands, etc.
