#21 is one of the best looking sealants on the market, IMO. Seriously a very underrated product, and if wasn't for the terrible streaking issues and long drying times (sometimes up to 2 hours before wipe away) I would probably have never discovered Zaino.
That said, Zaino looks better (but different) IMO, but not only that, but in terms of durability, its not even close. #21 held its look for 2-3 months and definetly beaded water tight durning that time, but after the 3rd month, it fell off quick. However, on occasion, it was still going strong 4 months down the road. Very inconsistant and kind of strange.
Zaino will look fresh 5 months down the road, at least. 7 months on my wifes car, and still beading like crazy and looking freshly detailed.
In terms of inital looks, I would say Meguiars looks more carnuaba and definetly darkens the the paint more. In terms of depth, its pretty close, maybe a slight edge to Meguiars. But in terms of gloss and reflection, I would give Z5 a huge advantage. It just looks sharper to me, like your paint x 10.
They are both good, but in for my taste along I would select Zaino based on looks. In terms of durabilty and performance, Zaino with out a doubt.