what is the main difference in performance from a metal yoyo to a bi metal yoyo?
Also what is the difference between normal kitty vs fat kitty string ? (in terms of playability which is better for slack and so on)
Theoretically, the way a bimetal works is that the yoyo can sustain rim weight while cutting excess weight from the body by using a denser metal such as stainless steel to create the rings. Therefore, with each bimetal yoyo you feel a little more power, a little more punch at the end of the string when you throw it down, and the extra weight makes some pretty stable yoyos.
As for the normal vs fat kitty question, obviously fat kitty will be a little fatter, and therefore have a bit more weight to it. This extra material creates a string that whips through the air just slightly better (imo) and grabs more easily, making your bind tighter.
Exactly this ^
I personally love bi-metal yoyos and fat kitty strings 
I don’t own a bi-metal yet so I’ll let others answer that.
Regarding string, I recently bought some standard Kitty string, some fat (1.5) kitty strings, twisted strings, ammo strings, and venom strings just so I can compare them.
Short answer, I like the ammo the best. They hold string tension the best, then seem to whip well, they’re soft, they’re just an all around great string. The Venom was a close 2nd place as they are nearly the same string.
The Twisted Stringz (I think they were Type E) are also good but they seemed to need more break in time before they would hold string tension quite as well.
Both Kitty strings seemed to feel the same other than the fatter 1.5 would bind more readily. I noticed that Kitty strings seemed to lose their “bounce” rather quickly. I’d put a new string on my yoyo and after 30 minutes when I throw a forward throw instead of feeling the hit the end of the string with a slight cushioned bounce it would feel like a brick on a wire. Boom! You’re at the end of the string.
Also, in my opinion, the Kitty strings didn’t hold string tension very well. I’d take the string off of my throw hand and let the string neutralize it’s twist, wind the string, THEN put the loop on my throw hand. I’d throw a breakaway and try to do a Jade whip and the string would already be twisted. That’s on the first throw after neutralizing the twist.
I was surprised at how much difference there is with different string brands.
I got destroyed over on reddit by talking about this, but i dont care. Kitty is crap. I hear SOO many people raving about it, “all the pros use it” its the best out there, Kitty all day!
I cant roll my eyes hard enough at that. Cause I, like you, have found them to die in an hour or two and lose their quality and sanity. No string should crap out THAT fast, THAT badly, yet be recommended by so many. I dont get it, nor will I buy kitty string ever again.
Sure its cheap, but. . . its cheap. Not a fan of cheap (not talking about cost, but rather quality and longevity)
I should not have to accumulate a pile of dead strings after a good hard play sesh.
/end rant
Ok so Bi-metals have more rim weight, makes them more stable, less tilt-y, and more power sustained in the sleep. Bimetal will return with more power to the hand than a monometal would with the same throw and bind. More expensive but more performance. Its undeniable.
Fat string bind easier but will give less sleep time.
Thin strings are a bit harder to bind in comparison, but will give even longer sleep times and far less prone to binding when unexpected.
Ill go as far as to say that a single cloud string could outlast an entire 100 pack of kitty and STILL play better than a new kitty at the end of it. That being said, the brand “High End String” from a place im not even allowed to mention (!) was excellent.
Kitty string is great. I have XL yellow and the tension holding is fantastic.
i saw cloud string haha 4 dollar a string … haha is it really that good? Yeah i have noticed that kitty wears out fast but i use one string per week haha. Don’t know if that is bad for hands or not i just dont swap out that fast dont like wasting strings left and right.
Cloud string lasts for a really long time. Much longer than they even state.
is cloud string worth the four dollars?
Depends on your preferences on string. Some would say absolutely, while others would say not. Buy one and try it. You tell us whether or not it’s worth buying for you.
Yeah, I know what you mean. Some of the guys at our local Yoyo club love Kitty strings. I know of at least one other guy in out club who absolutely hates them.
When I was practicing a lot (when I first started yoyoing last year) I seemed to go through 2 Kitty strings per night. Luckily, I had a 100 pack.
glad to know im not alone. 