Hi Brian,
You won't go wrong by having the Oberheim, their products are very good indeed .... an American company with it's manufacturing links with the Galantis (Viscount/GEM etc etc).
As far as drawbar modules go they are all 'much of muchness' ... and when you get down to it, none of them
really sound like a tonewheel organ in my opinion - not even Suzuki-Hammond's take on the Hammond Organ is up to the original tonewheel sound despite all the hype of 'physical modelling' or 'digital signal modelling technology' (I think that's what Suzuki call it) ... but they
are a very good alternative
Presumably, you were originally thinking of the Ferrofish B4000 module which I believe is extremely good for the money - unless you are going to make a considerable saving on the price of the B4000 by going for the Oberheim, I would stick with your original plan and get a 'new' product.
Either way Brian, I wish you luck on your choice and I look forward to listening to your performances using the module in due course .... take care
Mike