I also say - seperate bowls for portion control. By feeding in the same bowl, the one may be eating faster and getting more of the food - gaining weight.
The other gets only what left - loses weight.
We had 2 doxie's - male and female. Fed them from seperate bowls at the same time and they liked to lick each others bowls out when they were done. We did monitor to make sure they were both done first. If we hadn't, the female would have eaten out of the males's bowl before he finished. She ate faster - more teeth.