Your question is which camera will work best with a Mac - Any digital camera will work with a Mac that has a USB port. Your camera is essentially acting as a USB card reader when plugged into the Mac. That is all.
Now which is the best for around $250? That's a tough call. Cheapest isn't always worst, and most expensive isn't always best.
The best thing is to read reviews, try out in-store demos, navigate the menu and snap pictures to see how you like it's ease of use. I can tell you, while I liked the use of the Sony Cybershot cameras, east of menu & features, the wait time to snap a picture was painful. Took forever to charge the flash (and while using photo lithium batteries too). My experience is based on owning a DSC-P72 (4.1MP) and DSC-H5 (7.2 MP, 12x Zoom).
And while you can shoot video with a lot of still image digital cameras, don't expect the best video recording quality
I eventually had the desire to shoot amateur/pro and finally broke down and went DSLR a few months back with a Nikon D80 w/18-200mm VR II lens - never looked back.
Let us know what you decide on.
-Ian
My Shots