I think both games will be just fine. There have been similar situations like this in other genres, and there has never been any evidence to suggest that an XBLA/PSN game had any adverse effect on a physical product. To reiterate, these games are being sold through two different channels. There is no real rivalry between physical and non-physical games on 360/PS3. XBLA games by nature are smaller games made cheaply, targeting a casual audience.
It should also be understood that a physical game is, by nature of the beast, promoted far heavier than online network console games. Many of these downloadable games receive little to no promotion at all and certainly nothing anywhere close to the scale that a physical release would. So, physical presence and promotion is going to give a physical game an enormous edge every time. We just haven't reached the point yet where there is a legitimate concern about what effect an XBLA/PSN game will have on a physical product.
The last thing is, when game companies stopped developing football games after the EA/NFL disaster in 2004, the market all but disappeared from its once thriving state, but the gamers never did. They still exist and have just been waiting for more product to come along. In other words, there is enough for everyone to eat and get full. I think both projects will do well based on the size and scope of each since both are much smaller by comparison to productions created by large studios.
I said last year that I believe the football gaming sector of the market will find a resurgence through smaller independent companies and that prediction is certainly coming true right now as there is a healthy number of indies making football games right now when combining PC, Mobile, and Console projects and so far the PC and Mobile games have been making money. I don't know how well BCFX did, but I hope it's at least been profitable. The two other console games on the horizon doing well will be another huge step forward to resurrection. But gamers have to start buying. Gamers have more power right now than they've ever had to help steer the course.