As noted above, it is not particularly a room-size difference but a difference in things in the room (the studio in a lock-off has the kitchen-like area for the small fridge and microwave), and a number of the 2BRs on the outer-part of the U-shaped building have a larger area where the living room and sleeping rooms are, while a number in the inner-part are larger nearer where the room is closer to the entry door.
In choosing a lock-off or dedicated, main things to consider rather than size are: (a) the lock-off has two entry doors, one to the 1BR and one to the studio, and the dedicated has only one entry door before the kitchen area; thus if mainly children who can open doors will be in the second bedroom, you may want to choose a dedicated; (b) the dedicated has one-kitchen allowing for more closet space in the 2d bedroom, while the lock-off has the second small kitchen-like area with a small fridge and microwave, and second coffee maker; (c) the dedicated has two queen beds in the second bedroom, and the lock-off a queen and a couch/pull-out queen in the studio.