Personally, I would take the 3-15 even if all those other variables were equal. What happens when you want more magnification but you can’t get it? With a 10 power, that is far more likely to happen. With a 15, unless you’re shooting very far on smaller game, it is far less likely.
9-10x is good till about 600 yards for me. The argument that a guy could, one day, need more than 10x is valid to a point, but what are you guys doing for wind holds on these SFP scopes?? The holds are only accurate at max mag. Buying big mag range with the thought of one day maybe “needing” it, but probably never needing it, at the expense being able to hold wind at the most useful mag setting does not make sense to me.
Honest question, what are guys using these big magnification ranges for cause I see these conversations and think to myself I must be missing something. 6x gets me to 400 yds comfortably and I couldn’t imagine needing three times that for anything other than punching paper or steel at 1000 yds.