Re: 1/4 vs 1/8 click
There's an old rule of thumb that competitive shooters have used over the years regarding how fine the sight adjustments should be. It boils down to no finer than one-third the group size you can shoot. Finer adjustment per click increases the probability that you won't see the change with your next shot.
Olympic team shooters using 22 rimfire rifles like to have 1/12th MOA on their aperture sights. At 50 meters, one click moves impact about 1 mm. Before the international target size was reduced a bit, 1/6th MOA rear sights were the norm.
Benchresters seem to like 1/8th MOA clicks as they can center their 1/4th to 1/2 MOA groups to the target's center up to 1000 yards easier.
Highpower rifle shooters like 1/4 MOA for aperture sights through 600 yards and with scopes to 1000 yards. The US (and other country's, too) Palma Team shooting aperture sights from 600 to 1000 yards uses 1/2-MOA clicks on their rear sight.
So go out and measure some of your 15- to 20-shot long range groups. Then note how much 1/3rd their biggest ones size is; that's about the minimum you'll use effectively in the field correcting for wind and range settings.
When similar models of scopes have either 1/4 or 1/8 MOA value per click, the main difference is the 1/8 one has twice as many clicks per knob turn. This lets the maker keep the same mechanics for both scopes except for the ball detent ring on the adjustments. Another way to do it is to double the adjustment thread count per inch using the same ball detent assembly; this means the adjustment moves only half as far for the same degrees of knob turn.