M4/M16 is obviously more ergonomic in design, generally better in balance and manuverability, and with appropriate mods can be changed to your tastes of setup and add-on farkles more readily.

M14 is a classic long-gun with it's straight stock - relatively unbalanced, long, and heavier by a couple of pounds. It reminds me of my civvie hunting guns. It'll certainly make a man of you, humping it on the field all day. You could set it up with a G&P DMR style stock for a pistol grip if desired, or go for an EBR variant M14 if the pistol grip is a must for ergos or comfort... but it's still going to be long, and heavy.

It comes down to the environment you are using the gun at - if you plan on doing indoors and outdoors on a limited budget, go M16/M4. If it's outdoors, then it's more of a personal choice as to which gun type, and which variant you choose.

I got CA 180 round mids for $18 each, not that expensive and they work without problems.

Shinobii carries almost all the stock CA mechbox parts.

My team and I went to our field with all our guns and a long roll up tape measure, it was -5 C, there was no wind, We compared CA ak, G&G m4 , G&P m4 with lonex box , Cybergun ak, VA 36, G&G m16, Echo 1 m14, CA mp5, Thompson m1a1. guns had to chrono under 400 fps and hit a person once out of a 15 shot burst. The Echo1 m14 went out to 260 feet -30 feet longer than anything else. It was the full length version.

The reason adjusting the hop on the M16 CAN be tedious is due to the hop design.
Some have better arms, but the area where you want your hop to be is typically in it's most sensitive adjustment range, where the slightest increment on the wheel means a 4ft jump in your flight path.
Different chambers, different hop rubbers, different sensitivity zones.
They also have a very common tendency to dial back, but that's easily fixed by shimming the primary wheel.

The M14 has a better hop chamber design in general, much more stable, but even more annoying to adjust since you have to remove the mag.

If you want a DM platform, I highly recommend the M14 socom
If you want a general purpose gun, I highly recommend an M4
After years of playing with guns I find any barrel length past 430mm is just wasted length

The G&G/CA uses an AUG style hop up so it does not require removal of the magazine. It is accessed by pulling back the bolt, and even has a label on the mechbox plate saying which way is up and down. Functional bolt catches also help.

currently have G&G m14 ebr long. used to have an m4, and an m16. the m14 is a beast yet comfortable. very accurate, good fps and rof. tiring if in an all day game but i play shorter games so not an issue for me. the m4/16 is generally a lighter more compact choice and unlimited upgrades in and out. everyone has one, good if you need spare parts or borrow a mag, bad if like having something a bit different. think of style of game you play first...

For a G&G CM16 if you needed downgrade the spring so that it could meet a 350 requirement which spring would you buy? Also how can you tell in general which companies are compatible with your gun? I found that very confusing as a new player

http://www.airsoftcanada.com/showthread.php?t=4911 For the spring.

http://www.airsoftcanada.com/showthread.php?t=122837 For comparing different companies/brands. Although not complete and some info is out dated, still a very useful thread.

Thank you very much

off topic If you get a M16 there is alot of other guns that take the same mags future ref