I’ve chosen Amsterdam because the colors tend to be sharper and more vibrant. Also, it is relatively easy to find them in the more economical tubs, instead of the tubes.
When I’m mixing or diluting the paint I’ve often gone for the less expensive Pebeo brand for its better viscosity.
If you are working in a style that resembles impasto or using a pallet knife approach, then I strongly recommend using the Windsor & Newton brand in tubes, for the thicker and richest colors. These along with some of the Van Gogh brand are the most vibrant colors.
Warning: Do not blend on your skin, nor sharpen your brushes in your mouth. Many of the most vibrant tubes contain toxic materials like lead, zinc, and cadmium.
Note: Pebeo is easy to find in a private label brand at the bigger art supply stores. Take advantage of the price break when you can and when you are very confident of your color pallet.