Any 6M beam would probably perform better than any "stacked dipole". For 6M, 10ft high is 1/2 wavelength, and angle of propagation would probably be very similar to 10M. 20ft high is a full wavelength, and at that point (and higher), angle to horizon gets lower.
That said, propagation on 6M can be very unpredictable. I started off with a discone antenna and 10W in the 1990's. After 4 months of nothing heard, the band opened up and I worked steady contacts for over 2 hours with that antenna and 10W.
Another example, I have a 4 element beam, and had it pointed NW during the past CQ WW VHF contest last weekend (on FT8). I heard a G8 calling CQ off the side of the beam! I swung to north the best I could (limit of rotation), and worked the G8. I rotated thru south back to NE degrees (Europe) and worked a 9A5 station. After that, that path was gone, dead. Lasted all of 5 minutes up here in the north...
All VHF weak signal operation is horizontal, propagation is better with that, in most cases. My case with the vertical discone was due to a real solar "opening" happening. If you plan to work a lot of FT8, get a small 6M beam and a rotor on a short mast/tower/pipe/etc.
However, if limited to wire antennas, put up two if you can, at opposite orientations. That would give better chance to hear signals from different directions. Adding a vertical may help in a few, uncommon, cases. If you have a radio with dual receivers, plug two antennas in at the same time and try diversity receive.
Bottom line, 6M signals can be very unpredictable and sometimes surprise you. That is the interesting part about the "magic band". There may be cases where your simple dipole is just as good as anything else (not often, but possible)