I generally land on AEGs still being the king when it comes to actually playing games. For the most part performance is neither here nor there across the different methods of propulsion, but AEGs provide so many convenience benefits. Cheap easy to obtain mags, get a few decent batteries that fit and as long as you look after them you’re golden for years. And that’s it, maintenance costs not withstanding as it’s difficult to place where they land on a person to person basis (if you do all your own tech work versus sending them off elsewhere etc).
Keeping a stock of various pressure gasses gets, and stays, expensive. As good as the MWS is it has its limits with good performance once you hit certain low temperatures. It working, and it working well for a whole cold day are not equal. And as mentioned previously mags that come in around half a kilo each can take some getting used to, often resulting in further expense of having to improve the quality of your load bearing kit (which along side how expensive the gas can get is rarely mentioned).
HPA? Been there, done that, went back to AEGs (specifically the NGRS at the time). The line and tank were annoying to me, more so because it forces me to provision for something on my kit I don’t actually want there than anything else. The variety of CO2 stocks out there promising ‘HPA performance without the line’ are absolutely full of shit, if they actually functioned as they’re sold surely everyone would use them? CO2 simply isn’t, and never will be as stable as HPA… and that’s before you have to dick around swapping out a capsule ever half a mag, or paying an absolute fortune for 33g cartridges in the hope you can clear a mag before it puffs out. Then you’ve got the variety of HPA ‘stocks’ which are absolutely gopping.
I’ve used all 3. AEG is what I consistent come back to, the NGRS is great but the recoil actively irritated me to a point I sacked the platform off entirely. I love the MWS but mine is very much a back up, largely because I’m comfortable doing all the tech work on it myself. If I was anywhere near competent at teching AEGs I probably wouldn’t still have it. And the alleged ‘game changing performance’ from HPA is something I was left decidedly underwhelmed by, rendering my opinion that the biggest strength of HPA is the marketing behind them. For reference I’ve had a Fusion Engine build, 3 MTWs (2 of the OG billets and an forged) and a HPA’d Hicapa over the years.
I guess the point I get lost in your post is what it is you’re actually after. Seems to start off that you want a back up to a back up, but then switches to maybe a primary rendering something you already have as a back up to a backup.
AEG because of the benefits which have been covered and you’re well aware of? GBBRs for some realism you’re after? Or HPA because… truthfully I’m struggling to find why you’re looking in that direction from your post outside of everyone else is doing it? Seems to me you need to figure out what this purchase would actually be for, before narrowing down options from there and that’s not really something anyone on here can help with.