All depends what you are interested in, but dont expect a cuddly pet.
I have a few African, Indo-Australian hybrids, African monitors, and Australians, Ive had several monitors over the years from all 3 continents.
Ackies (V. acanthurus, V.acanthurus.brachyurus) are the best captives commonly available in the pet trade. If they were commonly available Storrs are great also, only smaller.
Here are red ackies the more expensive, prettier subspecies.
These are hatchlings, about 3 months old.
This is the second smallest species, a storrs, V. storri, a large male at 16 inches.
Of course if you are better equipped to provide much larger caging the best choice is also captive bred a flavi-argus cross, a bosc (American pet trade savannah monitor) is rarely ever CBB, in fact a few times in the US in the last 15 years by less people than you can run out of fingers counting on one hand. This is a flavi-argus, a hybrid between the V. panoptes (argus) and V.flavirufus (flavi), they also come in 3 way crosses with V.gouldi mixed in.
They are hardy, active, fast, eat almost anything, but never ever make the mistake of thinking they are cuddly.
If you have the space for a really big cage and consider just as more food than a flavi-argus, you could go with a large species, either way start with a dwarf, less damage, lower hospital bills when something goes wrong, believe me it can and does. This is a large species, there are many inexperienced keepers that get and keep large species, in the end its not good for either keeper or kept.
This is a blackthroat, V.albigularis. ionidesi, an African large species, they can get 5-7ft plus. This is the typical WC BT you find, only in bad health, never belive it means friendly, in fact this one was imported, hes healthy and dangerous also will get big.
Big, I mean big, this is a female, 6ft 4inches, a hybrid a BT/WT/ WT cross, males can get bigger.
Never make the mistake of thinking they are cuddly, Sobek and I have had an agreement from the start, shes a sweetheart to myself and a few others, not everyone, its her choice to be friendly to whom she wants when she wants.
