Again as above, 2 would be my limit.
I do think that you can easily get the best and the most out of both animals.
For me, the work I give my dogs, any lurcher of any type, should be treated as a jack of all trades but it's also a preferance to keep two differing types of lurcher.... it just makes life more interesting!
Though, each should be of different age, a few years apart, allowing for training whilst still having a 'made' dog to run, also, this makes for an easier time when dogs start ageing, again having one dog to run.
Just my thoughts