First the white plastic connectors are of minim quality and are not intended for use where they will be disconnected from each other routinely. Specifically, the type of pin that are used is not intended to be removed from the shell once installed. This may or may not be an issue but "one time incursion" type pins are typically not of high quality or reliability. On the other hand they are very inexpensive. Really, really cheap in fact.
Weather pack type connectors are intended to be used to disconnect sub assembly's (fans for example) from time to time and generally work well in automotive environments. I like them and intend to use them in several places on my SLC. The one disadvantage can be that they only have connectors with up to 6 circuits, with the exception of the big round one pictures above.
SOOOOOOOO......... I offer this alternative. They are plastic shells but use real professional grade pins in the connectors that can be removed with a insertion and removal tool. They also have really endless choices as far as pin numbers, sizes, shell configuration etc. and they are not real expensive like their mil spec metal shell cousins. They are a bit more expensive than weather packs however but worth it IMHO.
I am going to use at least one big one to connect the dash board harness to the chassis harness on my car. This will be something like 20 separate circuits. More than likely I will use two connections of about 8-12 each. One being a larger connector with a smaller number of big pins to supply power and another to run signal circuits like temp sensors.
Here is a example and a start point to do your own research. If you go to the catalog page you can begin to sort through the choices. Stay with the type 1 connector series and you will be OK.
TE Connectivity - 206037-1 - Circular Connectors - Circular Connectors - Allied Electronics
Maybe the best bet is to go to the Allied website and have a look. This is a very good source for electrical parts by the way. In many cases the min quantity will be cheaper than buying one piece from a hot rod store.
http://www.alliedelec.com/
Here's a good place to buy weatherpacks in quantity's that are useful to a complete build. You can piece each connector out and get just what you want.
http://www.waytekwire.com/products/20/Weather-Pack-Connectors/