Dallas vs. Houston

Which city is best, Dallas or Houston?
I'll be graduating in December. I would like to work in critical care.
I'm young and single so I'd like to be somewhere where there's a lot to do. I love the beach so I was leaning more towards Houston since its closer to the beach. I would of course like to be in a safe area as well.
Which city would benefit me more? What are some good hospitals and places to live in each city? Is the pay and cost of living the same?
Any information would be helpful...Thanks.