[SF-P90]

Being new to the sport I have been doing much research and at the moment these are my thoughts:

For CQB:
My preference is the TM TR P90! It's compact, easy to handle in the confines of a typical CQB environment, and it doesn't need any enhancements to shoot well stock out of the box. The Triple Rail also allows you to easily add scopes, laser pointers, and lights if that is your choice to enhance your playing style. In real life the P90 is becoming one of the mainstays of SWAT units (e.g. the Montreal's SWAT unit is a P90 user) and so if you are into milsim this fits well with that theme. BTW ... I have also seen that using a pistol only is a good weapon of choice for CQB but I have not done more research into pistols at this point.

For Outdoor Use:
My preference is the TM New M4A1! Being a M16 family weapon there are tons of enhancements and mods that you could implement on the M4A1 to make it a better shooter if that was your choice. Another reason why I pick the M4A1 for outdoor work is that most of the vests and BDUs are optimized to carry M16/M4 family gear. This is a more important factor for the outdoors since the games tend to last longer then CQB and you will need to carry more ammo and/or batteries. In real life the M4A1 is a weapon of choice for many Spec Ops Teams so using this weapon could fit well with a milsim theme.

In the end there are many good choices so pick the best one that you enjoy!