Some years ago I was in the same situation. I tuned the HW35, then bought a 97!
The main reason was I decided I wanted a .177 and the HW35 was a .22.
I don't think I'd sell a 35 to buy a 95 if the former suited my purposes. It's still a fantastic air rifle, to some it may look a little dated, but the performance is still very good with nothing to choose between the two on that score IMO.
The 97 does offer something else, it's amongst the most accurate full power springers ever built. It's weighty, that may be helpful if you're target shooting or not if you hunt. We all have a personal preference, do you fancy a 10 lb+ hunting rig?
As to barrel length. The 97s are all K-models, the 77 is available in standard and Karbine, whilst I think that the 95 is also only Karbine length in the UK with a screw cut barrel, supplied with a silencer/moderator. The latter makes the rifle a similar length to the HW35.
Barrel length won't have a noticeable effect on recoil, but it does alter the balance and hence muzzle flip.
Secondhand Standard HW35s fetch between £100-150 depending on the condition. So you'd need to put another couple of hundred into the pot for a new 95, which to me seems a poor return for little or no performance gain.
£50-80 will get you either a tuning kit or basic tune by an airgunsmith which should give clear improvements, and a rifle which is more enjoyable to shoot.