Avoid the M3D. Their motors are rubbish, cheap steppers with plastic gearing that strips very easily. Their motion system looks clever but is prone to binding (in z axis, which also affects y axis) and slop (in x axis due to the rack and spur gear setup). I also hear their support is pretty garbage.

I'd personally recommend against a mendel/i3 style printer purely because I'm not a fan of the motion system style. I would go for a replicator clone or the likes. They are solid and straightforward, easy to troubleshoot and calibrate. CoreXY, delta offer some moving mass reductions but can be a bit more complex to troubleshoot and calibrate, more so deltas than coreXY. They are great printers, but I wouldn't recommend them as a first printer. Although a linear delta's main advantage seems to be that it looks cool, I haven't seen them in industrial applications and I think there's a reason. That being said, I'm building and designing a printer and a large part of the reason I chose it is "it looks cool".