If I remember correctly, the reason the CTBUH considers spires as part of the height of the tower is that the spires are part of the architectural design of the build and as such will not change. Antennas, on the other hand, can be taken down or replaced by taller or shorter antennas making the height of the building ever-changing.
I would vote to use the height including the spire as the height in the UT forums due to the above reason - 374m / 376m depending on what is defined as grade.
To give an extreme hypothetical, imagine the spire on this building was replaced with a 1 sq-m floorspace room with a height of 77 metres. Technically, the roof height would be 374 metres, but this room would serve absolutely no purpose (other than maybe housing a really tall ladder
). So, why would that hypothetical room qualify as "roof" height, but an architectural spire not qualify to use as the total height of the building?
Horrible MS Word sketch of this hypothetical 77m tall room below!
View attachment 346663
Just my two cents.
Also, just pointing out that the "roof" height of the CN Tower is listed as 457m. I'll fight anyone who says this is the actual height of the CN Tower!! Hahahaha. The CN Tower is 553.3m tall, so help me god!