There are three kinds of artificial life in Mutant Future. Robots and basic androids are metal or, rarely, ceramic. Replicants are short lived living creatures made by advanced biotech. They melt after a set number of years (5 for most human appearing models). Synthetics are machines that result from knowledge of biology and the use of non-biological parts. They look and act like living things, even eating and respiring, but are not, at least in a narrow sense of biology. Here are some ideas for making synthetics unique. Most of these apply to machines as well but in different ways.

Basic and synthetic androids do not have mutations, they have upgrades. This means they can use parts they find to replace their existing powers with something else. In most games I would retain the limit of 3 "mutations" or apply rules similar to parasite mutations (penalties for powers) for those beyond the third. Synthetics have a leg up on machines in that they can use grafts as well as upgrades. They can implant or attach living tissue, thus allowing them to take powers from those they slay (or not, yech). Same limitations as upgrades apply.

Basic and synthetic androids can be rebuilt. As long as their CPU remains intact, they can be given new bodies or parts can be used to fix their existing frames. For synthetics, this means a reduction to no less than -10 hit points. For machines, they can be reduced to -25 hit points before their CPU is destroyed. They are treated as complexity 3 devices with a condition grade of 5 and take hours to weeks to repair (MF pages 42-43).

Basic and synthetic androids run on software. This can be hacked or otherwise altered. The results of this for synthetics are mental mutations or drawbacks. Basic androids get only drawbacks (with one exception). In fact most attempts result in mental drawbacks. As the androids are running on software that hasn't seen an update in many, many decades, they are already on the edge of catastrophic failure. Treat any attempts to alter their software should suffer the same penalties as rebuilding them. If a basic android has a clean reinstall of its software, something impossible for synthetics, then their memory is gone but they run much more effectively. Add d2 points to all their mental ability scores (or more if the ML wishes).

Other bonuses and penalties should include the android mutations I posted a few months ago: http://d-infinity.net/blog/derek-holland/expanded-android-mutations This is the expanded version with 20 more mutations than I posted to my Flesh, Blood and Fibers blog.