I have been running a TM P90 for 6 years, it fine outside so long as you are not playing on a parking lot. Range is slightly less than the average M4 but not enough to matter. Mine is upgraded to 385 FPS, so that helps a bit.
It is extremely short, easy and fast to bring to the shoulder to engage targets.
The hi caps can be troublesome, but I have had few issues mostly light maintenance and do not over load and you will be fine.
Mag pouches as noted are a pain very long and slow on the extract and reload. You really need to keep track of your ammo use.