Most of the judoka I have trained with are excellent on the ground, but training at BJJ as well as Judo can only benefit you as a martial artist because they specialise in ground work.
I train in Judo and achieved a 5 Dan. I have been training for 38 years. I have done a lot of travelling to different clubs, most of them do 50/50 standing & ground. Most of the judoka I have trained with are excellent on the ground, but training at BJJ as well as Judo can only benefit you as a martial artist because they specialise in ground work. Judo has a great transition from standing to ground, but remember an experienced judoka can put someone on there back fast and hard, but if they wish to can just as easily put you on your head. If it all goes wrong, as it is not a perfect world, the ground work is there.