My limited experience with the triple has been bad: the thermal design is poor so they break in expensive ways.
I like twins - heresy here I suppose - but I would turn to a Yamaha rather than the Kawasaki. Kawasaki has about the worst record for Japanese out of date model OEM parts supply.
One big reason old Hondas are popular is that Honda would supply parts for them pretty much forever. That's changed now, but they still have better support for older bikes than any other Japanese make.
A very few models - for example the CB750, XS650, and Z1 - have enough enthusiasts keeping them going that many non-OEM parts are available.
The Suzuki is a nice machine. Good record for durability (not a Z1 but not bad). The aftermarket parts supply is poor, Suzuki OEM parts availability worse.
Distributors (other than Honda), on factory orders, used to dump all parts a set number of years after a model was retired. Some would crush them to ensure destruction. Now they take the profit in selling them for cents per pound to businesses like CMSNL.com. That keeps them available but the prices reflect demand and stock - rare and in demand NLA OEM parts are, naturally, outrageously expensive.
The CB750, in my opinion, is the best choice if you plan on riding it a lot. Stuff will wear out: this one has the deepest well of aftermarket parts and some Honda parts are still listed (fewer every year of course). A good one will cost more than the others - price of popularity - but will probably hold its value better.
"Fully restored" covers acres of ground... restored to running, restored to "stock", concours level... what do you want? Asking for a fully restored bike suggests maybe you don't want a daily rider. If you want a "display" bike, pick the one that looks best to you.
