Lots of information at the below link. Look at chapter 2 for eligibility criteria and such.
While it has a low-ish interest rate (5%), is subsidized, and has a long grace period (12 month), it's a mediocre loan at best. It's administered through your school/ECSI rather than the official federal servicers, which also means it is not eligible for IBR/PAYE; you're stuck on 10 year repayment. In reading the rules of this particular loan, apparently you can defer it while in residency. However, you are unlikely to receive your entire loan balance as an LDS, which means you could only defer the portion that is LDS.
If you could get your entire professional school tuition as an LDS & defer it while in training so no interest accrues, yes it would be the best loan to have. However, the likelihood of that happening is low.
http://bhpr.hrsa.gov/scholarshipsloans/tools/guidelines/lds.pdf