I have the tack trunk you linked in blue (ordered it from Amazon). Absolutely love it, there is a leak in the barn roof right on top of my trunk and nothing in the trunk as ever gotten wet. My trainer and I each have one, we put one on each side of the main crossties so when the vet, farrier or whomever is there, we have good benches to sit on.
You can jam amazing amounts of crap in it, I have a half dozen saddle pads, 2-3 half pads, couple sets of boots, multiple girths, spare halters, spare bridles, bareback pad, couple sets of polo wraps, 3 riding helmets, half dozen pairs of riding gloves, first aid kit, couple bags of t-post caps and who knows what else and there is still room to spare.
I don't put my grooming supplies in it, tried that but they either became lost in the giant area or didn't fit in the small tray that is included. I have a separate tote with a stepstool that fits over it for my grooming supplies.
It claims you can put a saddle in it but I wouldn't do that. There isn't sufficient room to store a saddle suitably IMO.