I have both the Inch replica and Bosco Bell and all I can say is that it matters entirely on what you're training for. If you're training strictly to lift the Inch, then I would buy a solid baby Inch that is just at or slightly above your current strength level. My second choice would be the Bosco Bell and then you're set up to a max of 140-145lbs or so when loaded with lead shot.
The plate loaded Monster bell is really for strongman cleans and presses....and as such I'm sure can take a helluva beating...but it won't mimic the movement of the Inch. The sand loaded bell must have HUGE globes for it to be able to be loaded up to 200lbs because sand is not that dense of a medium....so I think it would just be ridiculously huge and meant more for strongman training.
The solid Baby Inch and Inch replicas can obviously take a beating. The Bosco Bell is not fragile by any means, but I wouldn't go dropping it on the floor from an overhead position or anything...it can dent and anything welded and not solid poured can always crack.
Since I really didn't use my Bosco Bell in a progressive manner....meaning all I did was load it to the max right from the get go.....I suppose I might've been better off just buying a Baby Inch at around 145lbs or so right from the beginning.
Richard Sorin usually chimes in on these threads and is quick to point out that Sorinex can make anything you want in any size....so you should shoot him an e-mail if you're looking for a loadable dumbbell.