I just went the opposite way, with trepidation. Why did I do it? After a few years of buying new bulbs you have spent the cost of an LED fixture, and there is just SO much more adjustability and coloration you can change with an LED Fixture.
What Ive seen so far (Only a few weeks after the changeover). At first the LED shimmer was offensive to my eyes. I got used to it. NO difference in growth or polyp extension, at least, none noticeable so far. Shadows with LED, there certainly is better coverage with T5. Algae loss with LED, I think as T5 bulbs age they may promote some algae growth. That observation might just be coincidental, but it times out with the lighting changeover.
Caveat, my tanks is LPS/Softie mix, not SPS, so mileage may vary.
I believe the T5/LED hybrid is probably where I will end up, just due to the better coverage factor of T5.