Ahhhh these questions!!! Like all other "whats the best" or "what to get" threads, you end up with what you have above, personal input. Simply that. Nothing is wrong with any of these opinions. What you will get is a Fact or 2 with personal experience.
Whats the quickest gun to upgrade? Depends what you want to upgrade, there are other upgrades then "JUST the SPRINGS"!
Whats the most durable body? No one can answer that. "TRY with facts" None of this, "I play hard and roll, and I've never broke myAEG." Machine Steel body, ok. I personally use TMs, all plastic bodies. I throw(literally), roll and land on my AEGs (250 lbs.) So conclusion is, TM plastic bodies are the most durable.
Price/cost. Ok if you set a limit, then thats it, you set a limit. Do research and find what falls in your set price range. REMEMBER do not settle for any AEG/Brand, and do not over spend, just for some extra perk/s.
So my opinion, if you want it done right:
*Spend years learning how to and working on AEG/ airsoft guns in general.
*During those years buy as many quality used AEGs you can. (this way you you get a feel for each & helps you make a selection on your final choice)
*Upgrade/tweek all those AEGs you've been collecting, taking a few at a time out to games, switching to another after each break.
*After realizing they all do the same F***ing thing, you'll go with either two choices: 1) the AEG you personally "like" most, based on personal opinion. or 2) the AEG you have collected the most Accessories and magazines for (and, preformes well)
*After years you now reach the point where you can make a "somewhat" final decision, but you still dont have just one favorite AEG.
*From those year you learned enough so that you can make most any AEG (except ICS, for me) perform better, last longer, shoot further/harder, then most any other for very little cost.
*In the end, you end up with what you consider your best (or one of the best) performing AEGs you built for $100.
Go with a brand you hear on these boards TM, CA, Echo 1 or whatever else :roll:
We all know your just going to end up getting what you want, and not what someone tells you.