Unfortunately, there is no "best" laptop. The names you see like Dell, Toshiba, Acer, HP, etc, they are only names. They are companies that pick what parts go inside the plastic case which they manufacture. The parts they pick from are all made from the same companies. The processors are made by either AMD or Intel. The graphics chips are either Intel, AMD/ATI, or nVidia. The RAM is going to be made by one of a number of specific companies. Same with the wireless, DVD drive, screen, etc.
It's probably more a software issue with your dell, or you chose a bad configuration (a slower model).
Also don't go for the Macbook comments. No brand is going to be 'faster' than anther. Macbook is not proven to run Vista faster than other brands (but it does run Vista faster than it's own OS, Mac, in some tests). Macs have the same parts in them as most other brands of computers, but they cost 3x more on average.
Make sure whatever you get has a dual-core processor and at LEAST 1gb or RAM. You can get what you want for between $600 and $800.