I think there are alternatives to most things, which is really great, so we pay our money and take our choice. My preference would be for the V-Slot as it appears to have a greater versatility of configuration but I suppose I would say that, wouldn't I ? Tweakie.
I've got a buildlog 2.x laser cutter and a enlarged Wolfstock delta 3d printer both made using Makerslide. They both work fine. However, I've chosen to build a 750mm X 1,500MM OX CNC router using V-Slot. Why? Two reasons: 1) V-Slot extrusions are available in up to 20mm X 80mm sizes. Makerslide is only available in 20mm X 40mm size. I want the extra stiffness that the 20mm X 80mm extrusions will afford me! 2) I believe (IMHO) that the actual V-Slot (internal V rail surface) is better for a CNC router that the Makerslide (external rail surface). Regards, Brian