Heavy Onagers rate of fire

[Didz]

I know heavy onagers have a much better attack against buildings, and a slightly improved one against troops as compared to vanilla onagers, but I've heard unconfirmed reports that they have a much slower firing rate as well. For those who have employed the ultimate in siege weaponry (by the time I've reached Heavy Onagers, I usually have enough standard ones that I don't bother), is this true?

No. At least I've not noticed any difference and I frequently have both types in the same group firing in unison.

Oh! Mind you I always use great balls of fire so they may all be firing slower anyway.