I am kinda surprised no one mentioned these factors. And it's cart for me... always.
1. The convenience factors...drink holders, scorecard/pencil right on the steering wheel...basket to hold towels, head covers, etc.
2. Probably the biggest reason I take cart only. The BS factor. I love to play fast. Me and my buddy will play 18 in about 2.5 hours and sometimes less. The BS factor is the ability to laugh, bust each others balls, etc... while in the cart. Walkers seem to be together on the tee box and sometimes walking together to their balls. But if one is way left and the other on the right... they split up. I've seen walkers on par 5 barely be together. I find the comeraderie of being in a cart way more fun.
3. Carts are faster. Don't give me the BS that walkers play just as fast. Can they? Perhaps. But I've yet to see 2 walker come thru us and yet we play thru people all the time. If we each bust a drive 230-250 yards out there... I can guarantee you my cart gets out there WAY faster than you walking. We play ready golf... we don't "cart hang". In other words.. if my ball is 230 out in the right rough... my buddy drops me.. goes to his ball that is 240 in the left center of the fairway. By the time I hit...I walk to where he is at and boom.. on our way.