Here are my thoughts on SMGs in MC5.
SMGs in MC5 are some of the weakest weapons ever witnessed in a Modern Combat title. Even if you played MC5 just a little bit, maybe even less than a day, and you used the starter SMG, the Sabre-S2, you will remember how weak that weapon is.
Submachine guns are supposed to form a niche in between shotguns and assault rifles, having mobility, damage up close, and handling. And in previous Modern Combats, SMGs were very powerful in close-quarters combat, and even out to mid-range. Two classic examples are the OPS65 from Zero Hour and the laser-beam MC81 in Fallen Nation. Those two weapons, along with their peers, had great close-quarter potentials. You could drop people up close surprisingly fast with the SMGs in close range.
However, MC5 definitely dropped the ball on them.
For instance, pretty much all of the assault rifles have the same rate of fire as the SMGs, with the exception of the Bramson and the initial burst of the FS80. And that is not how it should be. SMGs should have extremely high rates of fire, or have a lower rate of fire and deal good damage out to a good range. A classic example (not from Modern Combat) is the UMP45 from Call of Duty: Modern Warfare 2. It had an LMG rate of fire but with exceptional damage and range. And an SMG with an exceptionally high rate of fire and low damage should be similar to the Black Ops 2 Skorpion, because while it had low damage, it fired very quickly. In Modern Combat 5, most of the SMGs have the same ROF as the assault rifles.
Another thing I would like to point out is that the SMGs have the same rate of fire as the ARs. And they have much lower damage. They don't fire any faster than an average AR, like a UFIA PSD-2, Compakt-665 or Red-34, and they so severely lack the damage of the ARs. Couple that with MC5's terrible, inconsistent hit detection and all of the SMGs (with the exception of the nooby Bosk 3) kill very slowly up close. This means that even the ASIX-338 when hip firing will outclass a Fers09, Krube-37, Sabre-S2, or even an FS80.
Range of SMGs in MC5 are low, just like they should be.
So SMGs in MC5, similar rate of fires to assault rifles, lower damage than all assault rifles, and much lower ranges than the other assault rifles. The only advantages(and it is so minor) is that SMGs have over ARs in Blackout is that they have higher mobility. Otherwise, no advantage.
The only remotely competitive SMG in MC5 is the nooby Bosk 3. But no one else bothers to break out the Jolt or the Bramson.