The only differences I can recall is some do the extraction and I've not seen it on others. I'll confess to not ever having asked / checked properly tbh, but apart from that they're much of a muchness afaic.
If I had to choose I'd go Geberit, as I'd be looking for long term parts availability. That would be my primary concern.
Price wise there's not a big enough difference to argue, considering this'll be buried behind your tiles for the foreseeable.