I buy where-ever I can find the best deal. As my interests widen, I have to find more places to get things, EVEN if one of the places I frequent may also carry the same kind of stuff.
With that being said, my main sources of yoyos via mail order is YoYoExpert and YoYoBestBuy, but I will also buy from YoYoRewind. I even got 1 yoyo from YoYoSam because it was the best deal. My first go-to place is YoYoBestBuy, but that's because I consider JD a friend so I throw my business that way first, then I go to YoYoExpert.
For tops, with the exception of the chonkakegoma I got via SpinGear, it's been YoYoExpert and YoYoSam. I got a Sophia for like $70 on sale, and I can't argue that! Now that YYE carries the koma tops, I have less reason to buy those form SpinGear. I know YoYoPlay has I think bought up Spintastics. From what I hear, this would mean more tops. I have no issues with buying from them but I haven't yet. I can't complain about Spintastics gear and wouldn't mind owning another QSC in both bearing an fixed tip configs.
When it comes to boomerangs, it's pretty much "boomerangs.com".
When it comes to juggling, I'm being spread thin. House Of Poi has a lot of stuff, but then again so does Renegade Juggling, and so does YoYoSam. It's really depended on what I've chosen to pursue and what has had the best price. My latest YYS purchase was a set of Duncan clubs and some Play Sil-X Russia type juggling balls. I'm also currently researching other types of balls, clubs, devil sticks, flower sticks and poi. I do know I got my contact stage balls via Renegade, but I'm pretty sure the poi I am looking at will be form House of Poi. I've been strongly advised to look into GBallz for beanbag type balls, and once I justify the price in my head(they do them all semi-custom), I'll go for it.
YYS has been good. Since I really got into the whole skill toy thing, I've noticed them making changes under the surface and all for the better. As you've likely noticed, customer service is very high on the priority list for companies that carry skill toys. This year, I had an important email change and the only way I could get this changed was via directly contacting YYS and they quickly helped make the change happen. The biggest things I've noticed is that they've been more transparent, which makes tracking orders easier. Plus, the fairly frequent discount codes helps me explore these various interests and save money. Plus, I'm not the only one playing with skill toys and needing stuff, so saving money is always a good thing.
Currently, there's a sale going on with Kendama USA with Ozora kendamas starting at $10 and they got one I want to get 2 of in a bare wood at $15 each. No money right now, but if that changes, I'll get 2. I'm not big on kendama, but I do like the ozora models and at $15, it's a steal.