The attractive thing about adding some factory-painted figures to your ranks is that well, they are already painted so it can save you many hours of work. The downside is of course that not all paint jobs are created equal. There is likely to be a big difference in colors and level of detail across manufacturers, and also with your own painting standards. Then again, perhaps the time savings outweigh those differences, or perhaps you can actually buy enough factory-painted guys to create a fighting unit sufficiently large that does not need to include figures with another paint scheme so you avoid the issue altogether.
To illustrate the differences in paint colors and level of detail I have prepared a few shots of factory and hand-painted figures. Take a look and be the judge.
GIs (left to right): 21st Century mortar crewman, 21st Century infantryman, Forces of Valor, Toy Soldiers of San Diego (hand-painted), First Gear (Recent Britains Deetail Recasts), Original Britains Deetail. A wide range of colors. Quality-wise, the thing that I least like are the eyes on the First Gear figure. It is very easy to do a bad job on the eyes, and that's why I don't even try. Plus, at the distance that you usually look at them you don't really get to see much of the eyes anyhow.
Soviet: 21st Century Toys, Supreme Playsets (Italeri Recasts), Marx (hand-painted), 21st Century Toys, Supreme Playsets. The paint job on the Supreme Playset guys is really poor, except for the eyes, which are surprisingly well done. They probably did this to compensate for the sloppy job on the rest of the figure.
Japanese: First Gear, 21st Century Toys, Britains Deetail, Airfix (hand-painted). I have to admit that I like the paint job on the 21st Century figure much more than my own.
German Infantry: 21st Century Toys (initial series), Forces of Valor, 21st Century Toys (late series), Britains Deetail, First Gear. I don't know what they were thinking when they chose light blue for the Britains Deetail guys. Once I read that Britains Deetail would try to use only six colors on their figures, but in this case I don't even think that can be used as the excuse. On the other hand, the 21st Century guy in the middle is really among the best factory painted jobs and a real improvement over their initial series.
German Paratroops: 21st Century on left and right, Airfix (hand-painted), middle. The one on the left is wearing a cammo jumping smock. The one on the right is probably meant to be wearing the early war colors, but his colors don't really resemble those I found when I researched how to paint my Airfix guys.
Featured figures: 21st Century Toys US Infantry, Forces of Valor US Infantry, TSSD US Infantry, Toy Soldiers of San Diego US Infantry, First Gear US Infantry, Britains Deetail US Infantry, 21st Century Toys Soviet Infantry, Supreme Playsets Soviet Infantry, Italeri Soviet Infantry, Marx Soviet Infantry, 21st Century Toys Japanese Infantry, First Gear Japanese Infantry, Britains Deetail Japanese Infantry, Airfix Japanese Infantry, 21st Century Toys German Infantry, Forces of Valor German Infantry, Britains Deetail German Infantry, First Gear German Infantry, 21st Century Toys German Paratroops, Airfix German Paratroops