The IMG carrier is weaker for a one of several reasons, depending on who you ask. Here are the general answers;
- It is not manufactured by a particularly strong or warlike faction (Although, in many cases, they certainly act that way), and is therefore made more to what the faction can handle. In an OORP sense, it's a very versatile RP platform. Hell, the former ICMG RPed them as colony ships.
- It is somewhat more suited for travel in asteroid fields (which, to an extent, it is) and thus gives up some degree of power in exchange for easy maneuvering in such fields.
- It's spammed too much (not true to any extent)
OR
- TEH ADMINZZZ HAATE UZ (not true, either)
Personally...I go with a mix of the first and second options.