I own 2 Blacktails : a TD and a 1pc , they are both sharp shooters and real beauties, that's a real pleasure to shoot them. The 1pc is a litlle bit smoother, they are both deadly quiet with a dacron string and they are top performers : arround 175 fps@28" at 10 grains per pound with dacron, the mechanical efficiency is arround 82 %.
The main drawback on blacktails is that you have to wait 13 months to get one!
Great plain are surely nice bows too but more serialised and you have less possibilities to customize the wood choice.