I would actually suggest more time for Tulamben, probably taking 5 days, and 3 days for Padang Bai. Reason is Tulamben offers convenience of shore dives and boat dives via dugouts the locals call jokong, which itself is an experience. Tulamben is has excellent macro environment, not to mention the highly accessible USS Liberty wreck, and on season, even Mola Mola (Sunfish).
I like Tulamben for its diving assessibility. Literally, you can dive till you drop, five or six dives a day is totally doable. I did six dives a day for two days consecutively, starting the first at 6am.... Even night dive is an experience like riding in space, especially with the pitch black sand taking away one element of dimension...
As others have said, you have varied dive sites to explore in Tulamben, my personal favourite is the wall dive at Drop Off where I have thus far merely touched 36.5 metres, and still the bottom seemed a long way off.... Drop Off and Coral garden is a total photographers' delight....while USS Liberty provides the sense of adventure as all wrecks do...
Doing boat dives from Padang Bai means you will have limited dives...usually just 3 or at best 4 dives a day...
I would recommend Tulamben Wreck Divers for your trip. Accommodation is excellent, food is good, and the best part is the company....The outfit is run by Australians Tony & Dot Medcraft, the friendliest dive operators on earth. TWD resort is located right infront of the Liberty wreck..... so its more or less a house wreck/reef.... The Medcrafts also have villa accommodations for those who need more pampering.....
TWD staff are very accommodating and friendly. Very personalised service, more like having your very own divemaster to accompany your dives....and flexible enough so you decide the time you want to dive.... I don't get this anywhere else.... which is why TWD is my preferred choice in Tulamben...