Hello and welcome to HC!
I agree with JL, you've got to go with what your heart tells you. I personally would choose the chinesey as he's being neglected by being kept in a tiny cage with poor husbandry. However, this is just me so you will need to find which it is you have your heart set on. You may want to get the Russian since you have your heart set on him (if he's not from a breeder, the chances of him being a pure campbell is very unlikely)! Russians and Chinese hamsters are essentially the same care wise with both species being diabetes prone and fairly similar sized (though Chinese hamsters are much longer and slender and a Russian is stocky and short). A Russian will typically need a larger cage than a Chinese hamster as chineseys tend to be a bit more shy. However, this isn't to say a Chinese hamster should have a small cage as they can live in larger cages just fine granted you use your space wisely. All in all it's your decision so go with your gut! Good luck, and let us know which you end up choosing
Just a picky little bit here-
Different hamsters are known as species rather than breeds