Mungo, I don't have the 3 watt so I can't comment on them but my Mars2 works better than my 4' 6 bulb t5.ho fixture because light intensity is greater on the lower branches. With t5's you lose a lot of usable light as soon as you get a few inches away from the bulbs. Like you said tho, everybody's different. I still use my t5's, but only when the plants are short.
That is interesting that the Mars 2 give good veg, might have to give that a go..