Sorry man, but lots of what you've said is not true: The VSR is the most upgradable sniper rifle out there - many kits and many manufacturers. Prometheus/LayLax/First Factory/Nineball, PDI, ORGA, EdGI etc. - in fact, the VSR is such a famous platform for its hop that VSR buckings are what are used in many pistols as well because the cut of the barrel has been found to be ideal (almost all Tokyo Marui pistols use VSR hop up buckings). Along side AEG buckings, VSR buckings are the next most common in all of airsoft. Objectively the VSR has the most aftermarket parts available of any springer sniper rifle, but the Maruzen L96 APS-2 clones aren't far behind.
What brand 'metal trigger' did you buy? You realise most of these 'metal' triggers literally just have a metal outer casing but no internal upgrades. One should really only bother with the Airsoft Pro, LayLax or PDI offerings when it comes to the L96 triggers.
A second issue I take with the L96 is its magazine sits slightly further forward (only a few cm, but still) and that's the reason for its overall length being longer, but the inner barrel being shorter with the same overall length. The VSR is far more compact and practical in my opinion.
Avoid buying scopes with sniper rifles as they're usually gash and you want a decent clear one later on. I'd also say to not buy biodegradable BBs unless you shoot a lot (i.e. get through all those BBs in less than 3 months) - they're hygroscopic and will swell very easily. If your site allows non-degradables then pick up BBs that will degrade less and give you a consistent shot and leave less residue in the barrel.
What's the 'spring retainer'? The guide rod/spring guide? More powerful springs also need better sears too.
Again, I think it boils down to functionality. I really liked my L96, but it was pretty big even with the shorter and lighter PDI outer-barrel. Overall the VSR just feels more skirmishable, but both can be made to perform equally well.