I've personally used both timed tornadoes, thunder b's and a&k mkii pineapple grenades.
Personally, I'd say tornadoes were the best for coverage and were more reliable in terms of consistency. Where as the thunder b's, maybe 1 out of 15 or 20 wouldn't go off. However, they're still great grenades and I do like the surprising "pop" they give off.
And as for the a&k's, those weren't all that great. The timer on them is very unreliable and often went off as soon as you'd release them. They did have good a spread radius though and they look cool.