I did my CPL and ME together. For me the course I wanted to do (close to my home) was only offered on a twin and turned out to be cheaper than if I had done the course away from home on a single (though probably would not have worked out that way if I had needed a re-test/remedial traning etc...).
I guess the only noticeable differences being:
1) you're [typically] going 20kts faster; don't know whether this makes the nav easier or harder? Depends if you get lost I suppose (you're going to become more lost, quicker
). Personally, I find nav a bit easier the faster you're going (up to a point).
2) the emergencies section is focused on assymetric flight rather than PFLs. Again, horses for courses.
The only other thing to say is that you are (understandably) expected to know how to operate everything in the aeroplane that is presented for test (even if they aren't specific test items), so if you have a twin with a load of bells and whistles then it
may add to the workload. My examiner went to town on the autopilot and icing protection systems (both of which were only loosely covered during the course).
I would guess that it's six and two threes though the SE course should typically be cheaper (even more so if you need a couple of stabs at the skills test).
Good luck.