I have some experience with MP5A2 TLF made by CA. Never had any problems with that replica and my general feelings about it are more than positive. Until yesterday I had two of them at home - one mine and one of my wife's. I swapped mine with a friend for Steyr AUG, but only because I just prefer longer weapons.
To make a long story short - CA MP5 is a fine piece of weapon. Personally I'd rather recommend A2 instead of A3, due to great battery compartment inside a stock and the stock itself - it's far more reliable then the retracting one of A3.
Marui stock replicas used to be seen as most reliable, but I think the're losing it. Breaking of a spur gear happens more and more often, same thing is about ABS bodies. Whether TM's quality control sleeps or their machinery is getting worn out - I don't know. I just observe that more and more TM's AEG's get broken without a reason.
On the other hand - CA replicas always have been seen as troublesome. But my own experience denies it - as I said before: dwo Classic Army MP5s at my home and not a single problem with them. You just have to remember about few things - grease it before first firing and oil the hopup often (or swap it to silicone one).
And one more thing - the metal body. I used to laugh at this but now I know this feeling very well: once you get a metal body, you hate to return to ABS. That's why I bought recently M15A4 Rifle (by CA) instead of Marui's M16A2.
I would actually prefer the restractable stocks on the mp5. The Batt. sizes is not that great on the folding stocks, yet the weight savigns is great. That makes the Mp5 in a indoor field excellent. I loved using it indoors, Normal Vests are able to carry two mp5 mags in one magpouch designated for m16.
But if you start to mount heavier things on the front, then a fixed stock with the large typ battery will help even out the weight.
Otherwise if you want to have greater Batt. capacity , get a larger foregrip.
You will run into a wide variety of opinions here...here's mine, based on my own experience.
Avoid CA and ICS guns. They are not as good as Tokyo Marui. This opinion is based on seeing large numbers of local players buy them, thinking they are a good deal, and then junking them when they break a few months later.
Here in the MAA, we have around 60 active players. While some of the CA Mp5s are working, nobody who has bought a CA AR15 has a working one anymore.
As for ICS, their Mp5 is quick to take down - but that's about it. I've seen ICS "metal" (Pacific Rim pot metal) bodies break quite a bit. The ICS AR15 design, while revolutionary, has its own issues.
I would only recommend a CA gun to an experienced player who has the skill to troubleshoot problems and install upgrades to keep the gun going.
I wouldn't recommend them for beginners.
You will find CA/ICS fans out there...if you want to take their advice, feel free. My opinion is that CA/ICS guns are unproven and a waste of money.
I suggest you buy a stock Marui for your first gun. Keep in mind that all AEG's have the same internal design, and will function essentially the same. They are all the same caliber, and barrel length does not do much for performance (opinion based on extensive testing and field experience).
Get what you want - if you want an Mp5 or Sig 552, or even a FAMAS - get the gun you like. If battery capacity is a concern, get a large battery capacity gun.
Most importantly, play in games! It's the only way you can really decide if you like your gun, or even like playing Airsoft. If you look around, you may find local players who will loan/rent guns to you.