In a 10g tank, pygmy might do better. Keep in mind, though, many people have failed in successfully keeping pygmys with a male betta. Some bettas just wont tolerate a fish that gets less than an inch long.
I guess it is really either way. Pandas would be less of a gamble, though.
if he has been solo in the tank for a while he may become aggressive towards any other fish that is added.
if you go with the panda's i would suggest at least 4 they tend to do better in groups