It really depends on what your goals as a painter are and what you find easy to work with. What a competition painter requires from their paints is not the same as a sci-fi wargamer's needs. I like to work on a wet palette, mix a lot of colors, and do a lot of thinning and glazing. Personally I use Golden artist acrylics extensively, with select colors from other ranges like Vallejo and Secret Weapon. I have some GW and P3 as well, and I generally like them, but I tend to not buy them because they come in those nonsensical little pots.
If I had a friend who was just getting into the hobby and asked what paints to get, I'd tell them to get Vallejo Model Color without hesitation. They're opaque, matte, can be used for glazes, don't spill all over your desk if you knock them over, and have the biggest selection of colors available.