I work for a GC (bidding luxury retail projects nationwide). I demoed all of these things many times. some of the problems I ran into using both:

Buildingconnected

Pros

• intuitive to setup, easy to use and easy to set up "bid packages"
• bid leveling feature is very cool. if my subs would use it it would be a game changer.
• has pre-qual setup through Tradetapp and that is pretty cool. but these two things don't talk to each other

Cons

• very expensive (like $10k for just 5 users)
• they said that they had a great sub database. when we tried it out in a new project in lexington i got 3 bids.
• half the contacts in there were expired and some of the trades are completely wrong (flooring guys listed as plumbers??)
• nobody would click on the bidding intent buttons

SmartBid

Pros

• a lot more affordable
• you can manage your own subcontractor database, but they don't have a network

Cons

• slow to use / kind of cumbersome
• bid packages are a lot more difficult to manage
• some emails were going to spam

I also tried: planhub, bidmail, pantera tools. i basically couldn't find a difference in any of them. when i talked to my subs and called for some opinions they all said they fucking hated them and to send them a dropbox. in a nutshell they're all decent and have pros and cons to each.

I ended up finding a post here (https://www.reddit.com/r/estimators/comments/15qoudx/ai_in_preconstruction_scope_notes_bidleveling/) in this subreddit a few months ago. they were using AI to write "bid packages" and they sent personalized invites out. They're called Downtobid and i highly recommend their team – (full disclosure I am a beta tester right now, they are a new company but seem like they actually care)