g302 vs g402 vs g502

If you can't get your hands on those, however, I have used all three, and owned 2 of them, and can give you a good idea of what they're like and what they have to offer.

Overviews:

Logitech G302:
Shape: some edges, may interfere if you like a smooth sleek mouse.
Grip: Good for claw grip, but a bit small for palm grip.
Size: Smaller than the other two.
Buttons: 2 extra side buttons. A bit small and less firm, good if you like less noticeable buttons.
DPI: 240-4000, basically good for anything from an fps to a MOBA.
Software: Very nice to have and handy for having different profiles for different games.
Weight: 3.07 oz.
Extra features: Some sick blue LEDs that are programmable on the back
Price: 39.99 USD
Summary: A very nice mouse to have in general. A very good feel and a good upgrade from a cheap mouse. I would recommend this mouse if you play a lot of MOBAs because it has good DPI and is lighter and smaller, allowing for good claw and fingertip grips. If you are looking for a heavier, more versatile mouse, then you may want a different mouse. It is also good for its cheap price, coming in at under 40 USD.

Logitech G402:
Shape: Smooth and sleek. The most smooth out of the 3. May slip out of your hand if you use fingertip grip and you're super weak lol.
Grip: The mouse is taller and larger than the G302, so it is more optimized for palm grip, but claw and fingertip grips are also viable.
Size: Bigger and taller than the G302. read above.
Buttons: 4 extra buttons. Very versatile for binds and DPI switch.
DPI: 240-4000, good for anything but this mouse is optimized for FPS.
Software: Same as G302.
Weight: 3.8 oz, heavier for good precision, making it an excellent mouse for flicking.
Extra Features: not much, but it is very good at clicking super fast haha
Price: 44.50 USD
Summary: A very good mouse to have in general if you use a lot of claw/palm grip. It is really good for FPS games such as CSGO, as the heavier weight gives you better precision and clicking faster is also good for that. Using your arm/wrist is more optimal for this mouse instead of using your fingers due to its size and button placement. Otherwise, this mouse is good for pretty much anything but is really good at FPS games. Comes in at a good price and 4 extra buttons are always handy.

Logitech G502:
Shape: Smooth almost everywhere but is not uniform. Some parts are concave but there is no big noticeable problems.
Grip: Optimal for every grip (if you want to see why see weight)
Size: Slightly less tall than the G402 but wider. You can use any grip because the dimensions are good unless you have tiny hands.
Buttons: 7 extra buttons! making this mouse a swiss-army knife, as you can bind lots of keys. I can play a whole MOBA using only this.
DPI: 20–12,000 dpi. Bestowing the best sensor you can get at the moment, it is certainly a great feature. But who uses 12,000 lmao?
Weight: 4.2 oz, making it the heaviest of all the ones I've listed, but it also the most versatile as it comes with adjustable weights.
Software: Same as others, though you will probably use this a lot more due to so many features+buttons.
Extra Features: This mouse is full of them, such as being able to tune with your mousepad, and having adjustable weights.
Price: 68.78 USD
Summary: The jack of all trades. For mice, at least. This mice is great for avid gamers looking to conquer any game they play, with the great precision to fine tuning to adjustable weights, this mouse is all about you. Good for almost any grip and any game, you can put this mouse to good use. The only reason I wouldn't get this mouse is if you don't like how many buttons it has. (I'm a simple guy, so I like simple things, including mice) If you hold it the right way you shouldn't 'accidentally' press a button. The mouse actually also comes with little part at the base for you to rest your thumb on. It's great if you have fat thumbs. It is a bit overwhelming, which may be a reason to not like it, but it is certainly the most high-quality and versatile on this list. Great for any game basically. BONUS: Also has a really nice scroll wheel with different sensitivity/precision.

Final Rundown:

G302 | Buy if you are:
-on a budget
-looking to play a lot of MOBAs (reminder: not just for MOBAs, just good for playing them)
-Like to use claw/fingertip grip
-like cool LEDs
-looking for lightweight and simple mouse

G402 | Buy if you are:
-on a medium budget
-looking to play games a lot, primarily FPS games (reminder: not just for FPS, just good for playing them)
-like to use claw/palm grip
-looking for a smooth nice uniform mouse
-looking for a slightly more versatile mouse

G502 | Buy if you are:
-looking for high-end mice
-looking for max customization
-like lots of buttons
-looking for a mouse that can be used with almost any grip
-looking for a mouse that is good for almost any game

Conclusion: In the end, I cannot say what mouse is best. It is all personal preference. This is all done from experience except for the numbers like weight and price. Hope you enjoyed it and pick the right mouse!