I have both monitors and tegus (mine are paraguayan black and whites .. whilst my male teg is like a puppy dog, the female is fiesty and will only just let me lift her out of the viv, the male is happy enough to follow me round, wander the house, sit etc.
They are incredibly intelligent lizards and absolutely fascinating. The thing with reds is that they do have a fairly strict dietry requirement for much fruit and veg, B&W's eat mainly rats, mice, chicken etc, with occassional offerings of fruit.
Black throats are very nice lizards also, and most that I have interacted with have been 'quite' tame. They are also intelligent, however, in my experience are not as such, or as interactive as tegs.
I keep various varanids and all have their own temperament .. my argus is a hissing headcase, my ornate nile is like a puppy ....
If it were me and I were after my first 'big' lizard I have to say that I would go with either a savanna monitor or a B&W tegu.
I don't think that you would go wrong with either.
hope this helps
Carl