I think their biggest meeting room which served as the dealers room for comic con was probably smaller than most of the meeting rooms at the Marriott.
They have one large room (72' x 50', or 3,600 sq. ft.) that can be divided into three equal-sized rooms (24' x 50', or 1,200 sq. ft.). With theater-style seating, they maintain that they have room for 400 seats, or 133 for each of the smaller rooms. (One of the three rooms could be divided into two, but that wouldn't be a sensible use of that space.)
By comparison, our dealers room is 60' x 170', or 10,200 sq. ft.; the VGR is 28' x 53', or 1,484 sq. ft.; and our largest panel room (formerly the Art Show room) is 21' x 62', or 1,302 sq. ft.
It's not tiny by any means, but it wouldn't exactly be an equal alternative to our main events room (102' x 120', or 12,240 sq. ft.). It's certainly no panacea. The total capacity of the Hilton Garden Inn space would only be about 5-6% that of our total attendance numbers--not a particularly impressive number, at least when the goal is relieving congestion at the Marriott.