Two main differences, both related:\n\nOne, the Tasco scopes usually have 1-inch main tubes and many (most?) Leupolds have 30mm tubes. That extra 5mm means extra elevation adjustment before your stadia (the thing that holds the reticle) hits the side of the scope.\n\nSecondly, the Tasco has two adjustment knobs; one for elevation and one for windage. But the configuration is like this: One knob at 12 o'clock, one at 3 o'clock, and one spring at 7:30 to press the stadia against the adjustment knobs. It's a common configuration, but it means that as you adjust the windage, the elevation can change as well. Leupold uses 2 springs placed 180 degrees from the adjustment knobs - so a knob at 12 and 3, and a spring at 6 and 9. It makes the scope more repeatable as you make adjustments.\n\nIf all you want to do is sight in your rifle at, say, 200 yards and then shoot a deer or two a season, the Tasco will do just fine. if, however, you're dinging clay pigeons at 700 yards with a quartering wind you'll want the scope that can perform for you.\n\nA really simple test of a scope's adjustment mechanism is to shoot a 3-shot group at the center of a large piece of cardboard - right at a target dot. Then move your windage a few minutes of angle to the right - I like to move it 6 minutes, or 24 clicks on a 1/4 moa scope. Place the reticle on the same target dot, and press the trigger 3 times. Now adjust your elevation 6 minutes up and repeat, then 6 minutes left, then 6 minutes down. You should have a perfect square defined by the 5 groups you shot, with the group in the lower left being 6 holes and the others being 3. If you have anything but a square, or your ending group isn't at the same place as your beginning group, your scope has a repeatability problem when adjusted.