We go back and forth across the border at the truck crossing regularly with a 29' TT. We have Nexus passes and don't know if the northbound lanes are tighter for non-Nexus lanes, but it doesn't look like it. Going northbound is a piece of cake compared to entering the US. If you go through the Nexus lane into the US, it is extremely tight to get through and you need to get lined up just right before approaching the booth. The yellow steel posts have lots of scrapes in them.... At the southbound exit, they have a bunch of concrete barriers at the exit and it's like an obstacle course to get through.
The northbound truck lanes at Pac. Hwy are only for trucks. Southbound, sometimes when it's busy, they let RVs go through the truck lanes which is good because the exit is easier.
Come to think of it, I don't think I've ever seen big motorhomes at the truck crossing, just lots of fifth wheels and TTs and smaller MHs.
The truck crossing (Pacific Highway) is a lot worse than Peace Arch or Aldergrove. Have not been through Peace Arch for many years but we have heard that it is very good for RVs.
The Aldergrove crossing is quite easy. From I-5 you can either cut across on H street or you can go up Guide Meridian from Bellingham. At Aldergrove going southbound, RVs have to use the truck lane so it's easier. I think Aldergrove is the better one to use if you don't have Nexus.
If you are in the Surrey area or heading towards Vancouver, Sumas is too far east. Pac. Hwy is the closest for us so that's the one we use.
If you don't have Nexus cards, we highly recommend them. We often sail through when the lineup for regular lanes are backed way up.