Hi Corester,
The solution to your dilemna depends on where you use your instruments. It is usually better to get a dedicated groove box for 'live' sounding applications. They offer more on board flexibility and function ... a groove machines' drum pads for example are more robust and realistic than one triggered via software.
Also, you should consider that most rhythm machines like the ER-1 and MC303 etc, have, apart from expansion options, parent firm and 3rd party software support.
Find someone in your locale who is using rhythm machines in the nature you intend to ... a good source of information is usually studio owners. Diplomatically ask them for a tour of what they are doing and how. Most people will be glad to help.
Best of luck
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Vim