I think both have had their shares of issues, but I feel the last two iterations of BF have really done a lot to push fans away. (That’s not to say cod hasn’t)
Like Sean said, for me it feels like they have slowly been devolving away from what made 3 and bad Company so good.
I love Battlefield 3, and even 4 but the series feels like it’s been heading in the wrong direction
I also promise you the next BF will be modern, EA/DICE have a long history of following COD setting the year after it’s released. So we will see what they do there