Mostly would depend on the time of day. First thing in the mornings, I have seen a long line to transfer within the North terminal. The last time I did this I waited about 45 minutes to get through.

Now I use IRIS and then go through Fast Track upstairs. I think it is quicker. Also, the arrivals lounge is landside at the Sofitel so sometimes I will veg out there for a while, especially if the security lines in the morning are long.