You have mentioned he's looking at a VF1100 Sabre. I am assuming you are asking about comparing it with a modern sports bike.
To answer your question directly: The short answer is that a modern 1000cc bike will have significantly better performance than 30 year old 1000cc bike. In fact a modern 600 will probably have better power to weight ratio.
Rough comparison a 1980 GS1000 made about 100hp. A modern 1000cc sports bike will make nearly twice that.
A modern CBR600 makes about 100hp. However it's probably about 50kg lighter.
However your post and other people's replies raise a few issues. Yes modern bikes are lighter, faster and more reliable, they also handle better and stop faster. But they're also more expensive and not everyone wants a modern sports bike.
Maybe you should be asking your friend what type of bike he wants to ride. What does he want to do with it? If that's what he wants.. well that's what he wants.
A VF1100 was and still is a capable bike. But by today's standards it will be considered heavy, and it's handling and braking will be considered poor. Also as it's now 30 years old it's probably in need of significant maintenance.
Think: 589lb/100hp+ bike capable of >120mph with soggy suspension and crappy brakes.
My other thought is that if your friend hasn't ridden for a long time and his last experience was on a dirt bike he might be in for a nasty surprise. Big heavy 30 year old road bikes don't turn or stop like a dirt bike or sports bike. He'll learn that the hard way the first day he tries riding fast on a windy road or wants to stop in a hurry.
However... Provided your friend is realistic about this bike, maintains it, and rides it within both his and the bikes limits he'll be fine.
If he really is a novice. There are a lot of other bikes out there that are more learner friendly that will help him gain confidence and proficiency faster.