I'm quite fond of the
O. hummelincki. The skin texture and color is just about endless in its abilities, and the common disposition of them is perfect as far as the "pet" aspect goes. Day active, curious, and fairly bold. Unfortunately being a small-egged species is a big drawback. O. vulgaris seems to be very similar to the O. hummelincki, just larger, so I'd like to give them a try someday when I have a big enough tank and find a reliable source.
I love my
O. briareus, for its disposition is very well suited to my liking, but I wish it wasn't quite as aggressive as it is. It has never inked, not the least bit shy. Despite the
O. briareus' nocturnal tendencies mine is always willing to come out and play during daylight. It just doesn't have the interesting variety of colors and textures many other species do. On the other hand, I haven't seen any other species that show the sky blue coloration. I guess you could say it's unique in that way.
A. aculeatus shows some really neat behaviors I haven't observed in the other species I've kept.
You have to consider though that the ones we have kept are all individuals and their "personality" isn't necessarily representative of other individuals within the same species. And really what it boils down to is how much you enjoy their company. Isn't that the point of having a pet?
I've never gotten to keep a Bimac. No chiller on my tank and it gets pretty hot here in Texas in the middle of Summer. Maybe one of these days they will be more common once again. The large-egg aspect makes them very desirable.
If I could dedicate an entire room to modifying into a large aquarium and afford the project, O. cyanea would win hands down. Impressive size and skin displays, very much a day active species, could observe it from across the room and make out all the details. Maybe even dive in and hang out with it
Really though there are so many different species with unique characteristics it's hard to say realistically.