I also got NW's ESAM. I think these programs are very different, as there is not a single one in ESAM doing statistical related research, they are all using differential equations to model different things. So it really depends on what kind of research do you want to do. You said that both are fine, but I think you have to have a preference between these two actually completely different fields. If you like interdiscinplinary math, then go ESAM, and if you like any statistical related stuff, go wiscosin.