Hey, so I almost went into Urology so I can answer a few basic qs.
Competitiveness: Urology doesn't post its stats but it's much more competitive than EM. It's about on par with ENT, and EM is more middle-of-the-road.
Lifestyle: EM is shift work, but you will work a lot of nights and weekends throughout your career. Urology sees few Emergencies, but the lifestyle depends on whether you go into private practice (relatively good lifestyle) or academics (demanding lifestyle).
I have no idea about compensation and demand...I imagine EM is in more demand and Urology gets paid more in general.
Training: 3-4 medium intense years for EM, 5-7 very intense years for Urology (you can do fellowships after both)
The thing that ultimately made me choose EM over Urology is that I realized that I don't LOVE the OR (I like it a lot, but I didn't think it would outweigh the lifestyle). Also, I missed working up undifferentiated patients (most of your Urology pts come to you with a diagnosis). I also missed the other areas of medicine and handling crashing patients, critical care situations, etc.
Good things about Urology include a relatively broad practice base compared to other surgical subspecialties, better personalities than most surg specialties, and lots of toys (da vinci, minimally invasive, lasers, etc).
When it comes down to it though, you really just need to do the rotations and decide. For me, it took doing another sub-I in Urology to make the decision.