Hi Mark
Two different markets for two different boats, Taipan One Design, strong following in Australia, which as an option can fit under the F16 rules. The Viper, a purpose built F16, built specifically for that market.
As far as market competition between the two boats, I think it will basically come down to that, you will either want a boat to sail as one design, or without the kite I guess, you'll probably be attracted to the Taipan, but if you a purpose built F16 with kite, the Viper would be more attractive, thats my way of thinking anyway.
Regards