You have to decide that. You will get more magnification of course with the 10X but will loose low light viewing ability. Also, depending on how much you view, actually have the binos to your eyes, the 8X would be easier as far as eye strain. All things being equal,Divide the objective lens number by the power and you get a factor. Example, your 8X42s the factor is 42 divided by 8 equals 5+. With your 10x42s your factor is 4+. The best factor for low light viewing is a 7. This is because of the limitations of the human eye. The ideal bino for all day, low light, non stop viewing would be something like a 7x50. Coincidently, the size of the venable army binos of old. You have to decide what most of your viewing is like and a what ranges. Higher magnification is good and bad. Low power is good and bad. The average human can not hold anything larger than 10 power still enough to take advantage of the extra magnification. In my close quarters hunting and glassing I opted for the 7x42. Gives me a factor of 6, yet kept the binos small enough I can shoot comfortably with them on my chest. I'm telling you, buy the best glass you can afford. Consider it your last pair of binos if you can afford one of the top 3 and are willing to pop for the big bucks. Put them in dark places, I mean real dark places and the cream comes to the surface. I viewed and tested binos in all light conditions side by side out doors for 2 years in stores from Colorado to New York. When someone tells me his $200 binos are just as good as the big 3, I just smile and think to myself, he hasn't found his last pair of binoculars yet.[8D] Buy the best glass you can afford. There are some great binos in the $300-500 range. If you can afford $200, find a way to double it. If you can afford $500, find a way to double it and you'll have your last pair of binos. I narrowed itdown to 2binosLeica and Swarovski. The tie was broken with $150 price break on the Swarovskis. I've never regretted my decision.

And let me tell you, their service is fantastic. I lost an objective lens cover. I called to order a set, the girls said OK. I said you need a credit card number? She said, what for, they're free to Swarovski owners. Then she ask if I ever sent them in for service. I said why, the work fine. After 4 years all i had was little cut in the armoring. I then ask about their new screw out eyepieces instead of the pull out I had. She said, why don't you send them to us and let us go over them for you, so I did. They came back in about 3 or 4 weeks. New twist out eye cups, new armoring, new focus adjustment assembly, and yup the replacement lens covers that was all I wanted. The cost to me, shipping one way. I called to thank them so much. They said, just send them in every 3 or 4 years and we'll service them for you. Cost again is shipping one way.