SimonClass,
Upward curvature is based on the shape of the tunica (really, the CCs—not just the tunica). Erection angle, on the other hand, is based more on the attachment points. The crura insert into the pelvic bones (ischiopubic rami) and then head up toward the pubic symphysis. The susp. lig. holds the shaft against the pubic symphysis during erection. Since the pelvic bones are lower (closer to the feet) than the pubic symphysis, the erect shaft forms an upward angle as it exits the body as long as the susp. lig. is tight. If the lig is loose, however, the shaft does not stay tightly against the pubic symphysis during erection but drops down and forms more of a horizontal angle (or lower).
A penis does not have to be long to hit the G-spot. From what I’ve read, 3-4” (nbp) should easily hit the spot in the vast majority of women.
As for what’s more important, I can only answer for myself. I personally would rather have a larger penis than one with a high erection angle. But my point is that you don’t have to choose between them. Penis growth and high erection angle are not mutually exclusive. As long as you avoid low angle hanging, you should be able to have your cake and eat it too.
It should also be said that a high erection angle is not required to hit the G-spot. It helps when having face-to-face sex, but a low erection angle might work better in certain positions, such as rear entry.
Also, the G-spot is not the only hot spot in the vagina. There’s also the CDS. So, one shouldn’t necessarily design one’s PE program around optimally hitting the G-spot (if so, we’d all be aiming for 4” dicks with massive upward curves).
SO and OTS hanging should both work fine. I think more guys have gained from SO than from OTS, but that may just be because SO is generally easier to do, so guys tend to stick with it longer.