In general I would prefer a plain matte screen; works very well eg. in a Mamiya RB. However considering the dimensions of the screen i a 35mm SLR, I find a focusing aid such as a split image screen very useful. Yes, it can be annoying (particularly when the thing goes black - which happens all to frequently), but for critical focusing it's a very nice feature. So on balance (for 35mm) - I want the split image.