Are you *staying* in Taba the whole week? I mean, do you have to dive daily (wherever you choose) and come back to Taba in the end of the day?
Aqaba- I think it will consume too much time for you to get there and back: You'll have to either cross to Eilat and again to Aqaba, or get a ferry from Sinai (I think from Nuweiba- not sure about it). So the hassle and time consuming is not worth it.
Eilat is a nice option if you have a buddy and you prefer unguided dives. Dive sites are not as beautiful as Dahab's, but they are nonetheless rich with many things. Don't expect to see "big stuff" other than an occasional turtle, or an eagle ray.
However, crossing from Taba/Eilat takes only about 20-30 minutes, and Eilat has other things to offer besides diving. It is a good option for daily-based diving.
Taba has some nice dive sites, but you may get tired of re-diving the same 2-3 sites the whole week. There are also daily boats going to relatively near dive sites in the vicinity.
Dahab is probably the best option from diving aspects, but if you stay in Taba it will definitely tire you (and cost quite a bunch) to go everyday Taba/Dahab...
In my opinion you'll enjoy a vacation relaxing in Taba, diving there a little and a little in Eilat (and perhaps a day in Dahab will change your mind
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