We've done a lot of geo systems and always size for heating at 98% factor. That is, the coldest weather 98% of the time. The bottom 2% is short term and can be handled with aux heating. That said, we always install either multiple 1-stage systems or 2-stage units to help accommodate the difference between winter heating and summer cooling. Cooling is generally about 50% of heating in our area. Now our prayers have been answer with modulating compressors. ClimateMaster now has a modulating unit and I'm sure others do or will shortly. With modulation, you can size for heating and easily accommodate all the cooling needs with good humidity control as well. I suspect 3-tons is the cooling load and 5-tons is the heating load, as stated by beenthere. As such, I'd go with the 5-ton systems, 2-stage or modulating. If you go 3-tons with a 5-ton heating load, you'll be paying a lot more for heat with the aux electric heaters. That's generally not the preference for geo systems.
If YOU want change, YOU have to first change.
If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!