My alt is a doctor. Droid of choice is an R series droid (has an R5) with Med Module 6, Item Storage (up to 10 items), Food and Chem Crafting station and data storage.
The data storage lets you keep schematics in there and not clutter up your datapad.
The item storage is an excellent place to keep your droid batteries (let him carry his own darn food!) and your best crafting tools (items inside droids do not decay on death).
The med module part and crafting part, hopefully, are obvious.
Some people prefer probots because they are hardier, but I don't use my droid in fights or just leave it out all the time.
ALSO... be aware that the med rating of a camp, if you're in it, seems to override the droid's medical rating. So it's actually best to call your droid and exit the camp with him to do your work.