
Logitech G
G600 MMO Gaming Mouse
Customizable MMO workhorse, durable, but discontinued and pricey.

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Favorite sym: Zowie U2-DW. Best locked in feeling when playing. No other mouse has given me that feeling. Favorite ergo: Lamzu Thorn. For my hand size and grip style, it just feels so natural and comfortable to play with.
My hands are 19*10 and I found the Viper V3 Pro bigger than I'd like. I tried that Zowie U2 -DW and fell in love. The ATK U2 is a clone that I would recommend.
I have a very similar grip style and just got a Zowie U2-DW because I was sick of my mice breaking and creaking etc. basically wanted a well built one and they’re considered some of the best. Won’t ever look back I love the shape and it feels great. The lack of 8k polling in the real world is irrelevant
Fav two are Zowie U2-DW: plug and play, amazing shape, great coating, great clicks. If I had to nitpick the weight could be lower and the scroll wheel. VGN Y2 Ultra: bought this mouse to try a mouse shape similar to Vaxee NP01 (due to Vaxee price and price of shipping one to Canada). Very pleased with the shape, no creaks in my copy, great clicks. My only con with the Y2 Ultra would be the provided cable isnt flexible, but I have my own flexible cable to use for charging.
If the shape fits you it’s fantastic. It’s basically a better superlight grip-wise. If you have problems with the superlight (that aren’t minor) it will still be bad for you, if the problems with the superlight is only how potato it feels, the u2 is a straight upgrade.
You said he currently uses the Glorious Model O, look what it says underneath the mouse. If he has the regular Model O, go for the O 2, he will have a new mouse, that feels familiar. If he already uses the O 2, maybe go for something like a Zowie U2-DW, it looks similarly shaped to the Glorious but has a better sensor. Edit: Just saw there's a Model O3 already available, so you could get him that.
Zowie is a very popular choice among Counter-Strike E-Sport Professionals, it's an excellent choice but doesn't have any fancy features.
I'm not going to lie... I am doing the exact same thing. Different reasons though. I am 36, I play Valorant and CS2 (I've played CEVOp/CALi for CS:S and played many LANs in a previous life) every other Saturday. I have like 40 mice. It was fun trying out different ones. I just bought a refurbished Zowie U2 and Zowie U2-DW, and I am selling all of my other mice. It comes to a point where I spent more money on mice than time spending inside the game. It's now time for my to just enjoy playing for the few hours that I spend in Valorant/CS2. All of the mice basically perform the same. It's not like back in the day when I played with the Intellimouse 1.1, etc, you had to be careful about what sensor was being used or you couldn't flick too fast. That's a problem in the past for most mice.
I'm not going to lie... I am doing the exact same thing. Different reasons though. I am 36, I play Valorant and CS2 (I've played CEVOp/CALi for CS:S and played many LANs in a previous life) every other Saturday. I have like 40 mice. It was fun trying out different ones. I just bought a refurbished Zowie U2 and Zowie U2-DW, and I am selling all of my other mice. It comes to a point where I spent more money on mice than time spending inside the game. It's now time for my to just enjoy playing for the few hours that I spend in Valorant/CS2. All of the mice basically perform the same. It's not like back in the day when I played with the Intellimouse 1.1, etc, you had to be careful about what sensor was being used or you couldn't flick too fast. That's a problem in the past for most mice.

Logitech G
G600 MMO Gaming Mouse
Customizable MMO workhorse, durable, but discontinued and pricey.

VXE
R1 Series
Budget king: lightweight, great value, long battery life.

Hitscan
Hyperlight
Ultra-light (39g) for small hands; sensor is outdated.

Razer
Viper V3 Pro
Adaptable shape, optical clicks, but scroll wheel malfunctions.

Logitech G
G502 HERO High Performance Gaming Mouse
Durable, heavy workhorse with free-spin scroll; prone to double-clicking.

Ranked #1
Hitscan - Hyperlight

Ranked #1
Teevolution - Terra

Ranked #1
Razer - Viper Ultimate

Ranked #1
ROCCAT (Turtle Beach) - Kone Pro

Ranked #1
Logitech G - G600 MMO Gaming Mouse

Ranked #1
Razer - Naga Trinity