As above post said, VF is much more refined with the interior. I love the modular design they have now, everything is deep dish, and not to mention the much smaller steering wheel. Great touch! And lots of gadgets. It does make all previous models outdated by far. However, I am also not too keen about the Mazda 3 front and Hyundai/Toyota rear. But as a driver, u see the interior more than the exterior...
Power wise, if you get a VF SS redline, you can always put in OTR, full exhaust and a dyno tune, that will make it 343kw at the engine (275rwkw) if it is a manual. My car has those mods and was dynoed at APS 2 weeks ago by Luis on BP Ultimate and that's the figure. It beats the GTS factory 325kw figure.
However, if you do the same to a GTS, it will get a better result due to their Cam or Ecu setting etc, correct me if I am wrong, I never had a GTS.
E3 GTS does have lots of electronic goodies like the displays of all the parameters, damper control, blind spot alert, DRL, etc. If you are after those and the name or resell value, go for the GTS.
The Brembo brakes on HSV are great when new and shiny, but when the time comes to replace the pads and discs....oh my, do you have deep pockets? We are talking thousands of dollars here. Put it this way, when a Holden dealer wants to buy a 2nd hand HSV, the very first thing they want to look at will be....you guessed it, how much brakes are left on the car. If they are worn, not interested...Brembos. So I have been told at Barlow Holden.
After all it's about money, the purchasing costs might be similar, but the running cost is the bigger thing. eg. insurance... So it is up to OP to toss it up and make a call.