Okay, you can get that instead of the next update, then
Independent Alien - Being from another world, you have to have been able to survive the trip across space, so you'll probably get some environmental resistance, as well as a dormancy stage of some sort. In addition, being completely alien means people will have a harder time discovering medications and procedures to stop you. You also have to deal with the fact that earth life is unfamiliar with you, so your control my not be initially as strong as you had hoped. However, since you've done this to countless planets in the past, you adapt faster than normal.
Alien Weapons - lose the environmental advantage, but maintains the difficult fighting medically from above. You also have the additional drawback of ultimately being a pawn in some other races plans. For true destruction, you'll probably have to find a way to mutate past what they expected so you can turn on your creators. Being a designed weapon, you will probably be able to spread much faster and be much more deadly. However, your mutating out of control isn't in your design, so you may have fewer opportunities to grow in power.
Natural Mutation - Few advantages or disadvantages. The major drawback would be that your source could likely be traced, allowing the medical establishment to better fight you. The advantage is that you had to come from somewhere or some other parasite, so it is likely you will get a free animal vector or something similar.
Military Weapon - Faster and deadlier than normal, but also somewhat limited in your mutating potential. In addition, there is some group somewhere who knows a hole lot about you. You may have escaped from a lab, or been purposefully spread. Maybe you've been stolen by a terrorist group, or this was just supposed to be a test run. Either way, you're eventually have to face your designers, and they'll know quite a bit about what makes you tick.