If you consolidate your repayment begins in 30 days I believe. I don't know if you can defer consolidated loans. Assuming your law school loans will be 60-100k the rate difference on that 15k will make very little change to your total payments out of law school.
Once again, yes, you can receive an in-school deferment for consolidated loans, at least federal loans. Not sure about the private loans, but the Staffords I had for undergrad were consolidated right as I entered repayment, and then deferred once I entered my master's program a year later. I agree that it might not make a huge difference in the payment at the end, but why pay more than is absolutely necessary?