A few elements to consider:
- the bigger the objective diameter is, the more light it captures --> so an objective 50 of better 56mm/60mm is best. Maximum power set to 4-6x to make sure you see the full body so it is easier to put the red dot at the right place. It will also be clearer/brighter at lower magnification - as explained in previous message.
- illuminated dot --> the risk with cheap optics is that illumination is too bright for night shot. Typically reticle red dot set for night use, would be almost invisible in bright light. Also some optics will generate internal reflection of the red dots and it will blur in red all what you'll see in the scope.
- if you are using a light source, then it is different as any scope will work.
Where I hunt, we can hunt 1h after sun set, which is pretty dark -->I onIy use German/Austrian riflescopes - Zeiss, Leica or Swarowski (or S&B or Khales but I do not own one) for that kind of hunt. I do have Burris, Night Force, Vortex (non HD) they are far away in terms of light transmission, clarity, flare resistance, definition in low light. Low light is where you see the difference between best European optics and the rest. Same applies to binoculars.
Zeiss and Leica are coming from photography and they make the best photographic optics (some of these camera lenses are selling for +$10'000$) The picture taken on the moon were made out of Zeiss optics on Hasselblad camera. The pictures of D-Day on Omaha beach taken with a leica. Leica made the first 35mm camera) --> They have decades of R&D on optics formulas, glass, coating, etc.
Try a Leica Tempus red dot, and compare it to a Docter or a Burris Fastfire... the Leica is fully neutral in terms of distortion, color etc. wiht the other you feel you are looking through something.
Except for a few collector rifles, usually my riflescope worths more than the rifle it is mounted on. I do not want to miss and opportunity because I rely not on the best i can afford. I also use my Zeiss V8i 2.8-20x56 as a spotting scope to confirm sex/age of chamois when hunting in the mountains and then for red stag in the evening.
Sorry but, for instance, I cannot understand fellows putting +2000$ on a fancy wood stock, engraving, etc. and then put a 800$ scope on that rifle.
These best riflescope brands will give you and amazing field of view for he same magnification ( For instance a leupold V6HD 1x will give you 36m at 100m, a leica magnus at 1x will give you 44m)
Bottom line, If you can afford one, you should consider a 56mm Zeiss V8 or HT, Leica Magnus/Fortis or Swarovski Z8i riflescope.