Hi Ray,
Having started out with a bench top style, I plan to move to a smaller knee in the future. I think as Bob has outlined, it depends on the materials you are milling and the work envelope you will need. I find that I am constantly running out of the Y and Z limits on my BF-30, which is has a bit more travel than the G0761. The footprint of the machines should be close to the same for a given table size, so I do not see this as an issue. The major limiting factor for many of the RF type benchtop clones, is very limited speed selection (6 speeds) and maximum speed (not to mention quality issues). In a benchtop, my recommendation for Grizzly mills in this price range would be the G0722. Variable speed, larger table with bigger T-slots, longer travel, power X/Z feed get high marks. You quickly get tired of cranking the X and Z axis handle, and finish improve dramatically with a powered X feed. A limitation of the G0722 (and most bench top mills) is top speed of 1600 RPM, but this is really minor. Most knee mills have a significantly higher top end speeds (usually around 4200-5000 RPM). If looking at a smaller knee on a limited budget, I would say that the PM-935TS would be much preferable to the G0728 for not much more. If you need a wider speed envelop, get a small VFD like the Teco L510 (about $200) and go with a 3 phase motor. Another significant factor to consider is that single phase motors do not take kindly to repeated stop/go tasks common with milling, and can burn up their start capacitors. This is not an issue with 3 phase and DC drive motors, they also give more even power delivery.
Mark
