Which sale is usually bigger?

they are the same in terms of price drops

It depends on how they do the sale, but they both tend to have TONS of games... I've never really counted how many, but the summer ones tend to feel a bit bigger. With that said however there are constantly sales going on all over the internet that are for games that activate on Steam so you really should keep an eye out for those :)

Many of my best savings have not been from a Steam sale.

They're pretty much analogous. It really depends more on which games go on sale in conjunction with what you're looking for.

summer sale, because of hype

I think they're the same. Really depends on the games that were released at what time. Sometimes, a certain sale might seem more incredible than the last simply because there were enough older games to have the 75% off label. :p

amazon sale is bigger and prices drop a lot more.

i remember when i purchased dungeon defenders from amazon, the 2-pack was at 5$ while on steam it was at 6-7$ and other places had it at 6$

since then i trust more on amazon

It's not the size of the sale, it's how they use it. :)

The holiday sale has always been the better one.