okay how about a basic answer.
AK47 generally shoots better and is reliable. the sr16 and ak both use a large battery. the m4 comes with a small battery. the sr16 and ak are full stock. the m4 has the adjustable stock. the sr16 has rails on the front for accessories and the m4 doesn't.
TM guns are all reliable so it really depends on your preference.
MODT - Magnus Operator Development Team - tu fui ego eris