Ignoring issue of quality of scope and precision of the internal mechanics, side wheels have the advantage that you dont have so far to reach forward, and you dont have to take rifle off target to read the distance on the front end. If the bell is stiff, you can cant the rufle too. One of those fishing reel ties is very handy to assist for the front end and also the zoom ring to.

I have seen a ring that passes around the front end of a front paralex scope that allows you to read distance on a vertical plain but it is not a common sight.

The side wheel is undoubtedly easier to rotate back and forth to fine tune the image sharpness but with both, you should try and get into the habit of only focusing in the one direction.

By this I mean if you take a focus on a target clockwise, you may get a different reading if you then try to re focus in anti clockwise direction. This is especially true if your scope is low on magnification say sub 20 to 30 X.

This is to do with the depth of field - the minimum and maximum distance that the image will stay in focus for a given level of mag. It also relates to Fstop values but as the scope doesnt have an iris like a camera lens this is an issue that you have little control over

At 10 x mag, the depth of field will be deep. at 50 mag, it will be very shallow = more accurate range finding. On the downside, the image will be darker and the target more difficult to find in the first instance.

Also depends what discipline you are shooting. For hunting or hunter FT I prefer staying at one mag and knowing my mildot for all ranges. To assist, I make my 45 yard target just out of sharp focus so I know when I have hit or gone beyond max range.

For FT, I use high mag for ranging (say 40 x then crank it down to 20x for the shot.

I dont think you will have trouble with the Nikko and the side will is the more flexible of the two options IMHO.

However, it may be worth trying two or three of the same scope as one may just feel crisper and hits a sharp image more finely than others. They are built to a budget after all.

Styer