not sure about the other states, but rego in Qld is based on number of cylinders - so you pay more for a V8 than you would a 6 or 4.
So if that's the case in your state, then a 6cylinder is going to be the cheaper option for you
as to what model suits best, well that's really an open ended question, a lot of it comes down to personal taste.
The first generation models VB-VL (1978-1988) are the smaller bodied Commodores, which are good if you prefer a medium sized car rather than a large sedan. But they are getting rather old, parts are more difficult to find and they aren't so great on fuel etc. Need to look carefully for rust, crash damage etc. Available with a 4spd manual or 3 spd trimatic auto. The VL was released with a fuel injected Nissan 6 cyl (very good engine, but tend to have electrical problems) 3 spd auto and 5spd manual. The VK was also released with an EFI 6, but it was the first of the EFI engines for Holden, so wasn't the greatest of engines. Unless you particularly like the early girls, and don't mind getting your hands on the spanners, I would suggest avoiding them now as most need work, parts availability isn't the greatest. But hey I've got one, wouldn't swap it for anything!
VN-VS are the second generation 1988-1997. 4 wheel disc brakes on all models standard. Larger body, available in fuel injected V6 & V8, available with a 5spd manual or TH700 4 spd auto. Both engines were very good. Good power, reasonable fuel economy (especially the V6). Whilst the locally produced V8 is a smooth engine, the V6 is an inherently a rough, harsh engine (particularly early VN) - but fairly reliable and make good power. The 5L generally remained a trouble free engine. No major flaws with the cars, just annoying stuff like oil leaks, rattles, water leaks etc. Any engine dramas present with the early V6's would be rectified by now. I would suggest however avoiding the early VN's. VP onward were available with independant rear suspension and climate control was offered on higher end models. VN-VR had the Buick sourced engine, VS had the 'Ecotec' V6 - which was basically a more refined version of the Buick, but does seem to suffer from some overheating issues. Originally they did have oil consumption issues, but most of it was sorted while they were under warranty. Parts for some of these models are also becoming difficult to find due to their age. VN brakes are terrible, VP wasn't much better. But the brakes are easily upgradable these days
VT-VZ third gen 1997-2006. VT-VY retained the Ecotec V6 with some further power increases and refinements. All models were released with new twin spot brake calipers and an improved master cylinder which really stepped up the performance of the brakes. The engine was a bit underpowered in the bigger body. The 195kw 5L V8 was available in the first model VT, but later model VT's introduced the American sourced alloy 220kw LS1 5.7L engine, which had more power. VZ introduced the new Alloytec DOHC alloy V6. Opinions are divided as to whether it is a better or lesser engine than it's predecessor, but on paper it made significantly more power, used less fuel and it never really had any major problems. No major problems with any of these models. Like the VP-VS, the IRS rear suspension does have a bad habit of prematurely scrubbing out the inside of rear tyres, particularly on lowered cars (the antiquated IRS design was really showing it's age) Like most GM auto transmissions, they are not the greatest, but reliable. And like most model Commodores, probably best to avoid the first year model as they were sorting out the bugs at the time. And if you plan on buying a LS1 powered VT, better off avoiding the VT, as that particular engine had a lot of serious problems, which may or may not be rectified by now. Better off going with the VX.
Which brings us to VE. Very BIG, heavy car, so if you don't want a barge, better off sticking to the earlier models. Unlike all the previous model Commodores, it's a clean sheet all Australian design (not based on the German Opel). It's a very safe, solid car - great chassis, very good independant rear suspension setup (far superior to the VP-VT setup), and a good front end too. The HSV models handle incredibly well considering their size. Available with a more refined version of the Alloytec V6 (latest model has direct injection) and the 6L V8. Biggest criticism of the VE is the bulky A pillar which really blocks the drivers vision, creating a major blindspot, along with complaints about the harshness of the V6 and the usual criticisms of the GM transmission. But overall it's a highly acclaimed model. I'd love one myself if they weren't so bloody HUGE!!
