Things to think about: What do you want to be able to do with the machine? What features do you have on your "usual" machine that you can't live without?
Two weeks ago I bought a Janome AQS2009 to take to classes, on weekend trips to fishing camps (DH fishes, I sew), etc. According to the dealer, she takes hers with her on plane trips in a cloth bag and puts it under the seat in front of her. I plan to do the same :).
Love it-has a nice bright light (does the mini have a light?), push button as well as foot control, and needle up/down, which is great for piecing. Has about 20 decorative stitches (less than the Platinum 720), but you can adjust the size of the zigzag (which I don't believe you can do with a Jem) and change the needle position. It's pretty compact and only weighs 12 pounds.
The price of the mini is certainly appealing! Good luck with your choice!