Rifle scopes compared on the spec sheet, with the maths the sheet leaves out.

Buy first focal plane if you will hold over or range with the reticle at any magnification other than the top one, because the reticle's marks stay true across the whole zoom range. Buy second focal plane if you mostly dial the turrets, or if the scope tops out around 10× or less, where an FFP reticle shrinks to a hair at the bottom of the range. Below 10× the choice is about reticle size, not accuracy.

Neither unit is more precise. A 0.1 MRAD click moves the point of impact 0.36 inches at 100 yards; a ¼ MOA click moves it 0.26 inches. Both are finer than anyone shoots. Choose the unit your reticle, your ballistic app and the people you shoot with already use — and never mix them. An MOA reticle over MRAD turrets means converting on every correction, and that is where misses come from.

Less than the number on the box suggests. A deer at 300 yards is a comfortable shot at 6× to 9×; hitting steel at 1,000 yards needs 15× to 20× to see the target well, not 35×. High magnification buys identification and spotting your own hits; it costs field of view, exit pupil, and a wobble that grows with the image. Buy the bottom of the range for the shooting you do most and treat the top end as a bonus.

Adjustment travel, mostly. A larger main tube gives the erector assembly more room to move, so a 34 mm scope can usually dial further than a 30 mm one and a 30 mm further than a 1-inch — which is why long-range scopes moved up in size. It does not make the image brighter; brightness is set by the objective and the magnification, and the tube is not in that equation. What a bigger tube does cost is weight and a different set of rings.