The best security is in not telling anybody what you have or where in the house it is...As far as safe brands, I've always personally liked National Security (I still have one to hold what's left of my meager collection), but I've sold far more Champions than any other line...Champion has an extensive list from small & basic to large & fully equipped...
Lots of things need to be considered including where in the house it (or they) will be installed...Will it be a showpiece you'll be tempted to show visitors or (like mine) hidden in a closet?...Can you physically move it through your entry door and navigate it in the house to where you want it?...It it's hidden away, will there be adequate lighting and elbow room when you want access?...
Temporary rental space is possible, but most gun stores with secure storage don't have room for it...If they do have room their inventory is down and they might be tempted to sell yours...Most people who store away from the house just park their safes in a self-storage unit and pack old furniture and mattresses around them...
Some things to stay away from when choosing a safe are square corners (they're spot welded and can be opened with a twenty pound sledgehammer) and doors that don't have bolts on all four edges...Don't worry about external or internal hinges; with bolts on all sides, it will only open when you want it open...
Don't worry about moving the safe(s) to another house, safe companies will move them for a price and they are well worth it...Also think about ventilation to prevent rusty guns...Small fans can be installed to move air and always use one or a few heating rods (usually 85 watts) in the safe...Just raising the temperature inside the safe one or two degrees will drive out moisture...
I'm sure I'll think of more later......Ben
The future is forged on the anvil of history...The interpreter of history wields the hammer... - Unknown author...