Never been to a "small island in Asia", but I've been to afew "small islands in the Caribbean", and I would not recomend a liter or 600 sport bike to ride on those specks. Scooters, and smaller MCs are the best way to get around them. Beware the locals it gets rough in the "cities".
Plus, the local tobacco products tend to reduce you reaction time, a very bad thing on a liter bike.
Don't let a time constraint affect your decision to buy a bike. If those are the only two bikes on the island and you can't get more shipped in, take the big bike. Otherwise, take the time to figure out what you like.
I think you should just go with the 600. It has plenty enough horse to keep you happy, and the 1000's tend to scare people. Most people don't even use all the power of a 600, let alone a 1000. There is no where other than a track that you will use 160+ horse, besides the 600's go 160 mph, which is plenty enough.
Jokers are everywhere. Fact, most people don't have the skills to operate todays litre class bikes as they are intended. Fact two, islands tend to be limited in open road travel. So, why buy a bike that you'll never be able truly thrash? Just going for pimp factor? Last fact, insurance laws are different across the world but one undeniable fact is that c.c. size rules the industry. Lower the c.c., lower the premium.
BUT I DO KNOW WUN THING, HOMIE: NOTHING WILL WHEELIE LIKE A GSX-R 1000. DON'T LET ALL THESE PUSSIEZ TELL YOU A TINY ISLAND IZ TOO SMALL TO DO WHEELIEZ ON- ALL YOU NEED IS A BLOCK OR TWO, UNLEZZ THE ISLAND YOU'RE TALKING ABOUT IZ LIKE THE ISLAND IN A NEW YORKER CARTOON WITH ONE PALM TREE ON IT AND THREE COCONUTZ. THEN MAYBE YOU DON'T REALLY NEED A MOTORCYCLE, BUT A LADDER.
SERIOUZLY, THOUGH, IF YOU'VE NEVER RIDDEN A MOTORCYCLE BEFORE, MAYBE YOU SHOULD SPEND THE FIRST FEW DAYZ ON THE CBR1000RR WITHOUT PUTTING A PIPE AND POWER COMMANDER ON IT FOR SAFETY'Z SAKE.
We need more information on your island, and the types of riding you'll be doing. If there are no highways, racetracks or backroads with clean, smooth pavement, I'd steer clear of sportbikes altogether. If you'll be riding short distances only, around town and on bumpy backroads, get a dirtbike and put street wheels on it . . .
Always buy local, as local as possible. Try to get your hands on an only-slightly used model. Make sure it's a make that's popular with the local delivery boys and taxi riders. Such locally popular models will be cheaper for parts and the neighbourhood mechanic will know how to fix it.
Never, ever get a big fat Yank mobile. It'll be the end of pleasurable biking. Such a machine will come to own you, instead of the other way around. Youll worry about it when parked. You'll draw attention to yourself. It might even be thrashed, laughed at, extremely expensive and a target for mild-mannered thievery and defacement.
When you're away from your bike, you don't want anyone to be able to tell that it belongs to a non-local. Your bike should blend.
That being said, try to get the coolest, biggest, fastest local model available, and then customize it to the max. Try to join local boy racer clubs, too. Jap has some pretty cool top-end machines. Kor has one or two, too, but they arent widely available yet. Elsewhere in the Orient, just ride whatever the local cops ride.