I used three sizes in my kitchen--3 3/4", 6 5/16", and 12". It just depends on how big the drawer is. Get a few pulls in a variety of sizes, have someone hold them up to the drawers and try it out. Personally I wouldn't use the very common 3"--the 3 3/4 are more comfortable.

The best way to search for info from gardenweb is to use google and type in gardenweb plus what you are looking for i.e. pull size, white cabinets, backsplash tiles etc. You should find lots of information. The search button on top of the gardenweb pages does not work well. Here's a link to get you started: Pull sizes

I agree and this is a good pic to explain pull layouts not only IMO should they be in proportion to the cabinets but sometimes it does not work to have them all installed in one direction. I choose pulls at the end of kitchen installs and often take a long time to figure out proportion and how all the pulls will function once installed so they do not hit each other . I use Lee Valley stainless pulls since they come in many sizes

The drawers are close enough in size that the pulls could all be the same size and look good. But if you have any doubts about which size pull, you can either make aluminum foil pulls in the two sizes and hold them up against the drawers, or you can buy one of each size of the pulls and see how they look. That should not be too expensive. Some of the hardware websites such as Top Knobs, allow you to get 2 or 3 samples, and then when you place your order you receive credit for the sample items you did not keep.