For Steam I normally use SteamDB, https://steamdb.info/sales/ sometimes a deals site like GG Deals to look at store comparisons.
This "Winter" sale is not good, not much to any change in discount percentages. For those who don't know, some digital game prices have been raised by publishers. This was also a recommendation made by Valve.
The sales leading up to the Winter sale, is almost better. As I always say, wishlist, and wait, don't rely on sales campaigns.