Hello Bachus
For Live work I would think the Wersi Ikarus would be better as it is lighter to carry around then the Abacus.
I currently run OAS 6 on my Abacus, (Will be updating later in the year) and so only have a limited knowledge of OAS 7, but double check to see if the VST instruments can be stored in Presets, (Most functions of OAS can be) as if so you will not be limited to the same 4 all night.
Also check what separate VST Hosts are available, as some can be run as VSTs themselves, which means you can expand the number of VST Instruments available to you.
Finally please remember that each VST instrument requires processing power (CPU) and this is what will limit the amount of VST Instruments you can run simultaneously.
Can’t remember the name of the DSP cards used in the Mediastation, but they were Not made by Lionstracs, and were of high quality. BTW. Wersi use Creamware DSP boards.
Hope this helps, and don’t forget to post about anything you find at the MusicMesse.

Bill