Had a BF30 bench top mill for a number of years, go with a 2 axis system and a quill DRO. Never found the need for a 3 axis DRO, unless you use the third axis for the quill (which make installation very challenging and cumbersome if using a glass scale). I had and Acu-Rite 2 axis with a separate vertical quill DRO that worked very nice, but that was back when they were less expensive and Enco had there 20% off sales. Most DRO's these days are quite good, really comes down to features, display and the type of scales you want to use. It is hard to justify the premium for magnetic scales, although they work very nicely and are a bit easier to install then glass scales.