Both MT's and OC's artic's seat either 56 or 58 depending what year they were bought.
Having ridden VanHool, NFI and NABI artic's I can say VanHool is the winner.
NFI and NABI buses give you a rollercoaster rider compare to VanHool bus. I use MT's artic's almost on a daily base and the VanHool couple times a month and this allows me to do a real comparsion between both buses.
Cannot find the numbers for VIVA Blue line, but it around 15,000 and that was before the final extension was open for it.
MT route 19 which is like the Blue line is suppose to support 23,000 riders, but based on my data numbers, it is around 30,000.
MT ridership numbers jump 2.5 million within 3 months in November as the new numbers were based on current date numbers. One reason for 19 to operate with close door 7 day a week now.