I'd go for the Futura 133.
With your sail sizes (8.3/7.0) and at 77 Kg. (170 Lbs.) I don't think you would find significantly more early planing on the Futura 144.
If you had a 9.0-10.0 m2 rig, then I think the additional width (77.5 vs 76.0 or 1.5 cm) would get you planing earlier, but with the 8.3 as your "big rig" the Futura 133 should get you going within about half a knot of the 144.
Sailing on fresh water is a consideration, for sure, but the additional volume would not help very much without the bigger rig to power it.
You will find that the additional top end range of the 133 is more significant than a minor gain on the bottom end/early planing.
Hope this helps,