XVR1 v B5 & B4
Having had both in house, the XVR1 is a little more versatile in terms of different slopes and balanced in and out. B4 allows for L/R, which the XVR1 does not. The sonic differences are slight enough to be a matter of taste. Extra versatility of the XVR1 is especially handy if you are planning to replace it with passive components later.
B5 is specialized for open baffles, with limited slopes in comparison to the B4, a bass boost as required for open baffles, and some eq for full range drivers. Same basic signature as the other two.
Having had both in house, the XVR1 is a little more versatile in terms of different slopes and balanced in and out. B4 allows for L/R, which the XVR1 does not. The sonic differences are slight enough to be a matter of taste. Extra versatility of the XVR1 is especially handy if you are planning to replace it with passive components later.
B5 is specialized for open baffles, with limited slopes in comparison to the B4, a bass boost as required for open baffles, and some eq for full range drivers. Same basic signature as the other two.