Whatever configuration appeals to you, you should consider strength, portability and comfort when shopping for horses. Most complete horses and better leg-only models, whether wood or steel, are sturdy enough for just about anything you're likely to throw at them. Leg-only models can also shoulder heavy loads easily, although it's up to you to pick out a 254 or 256 without a lot of knots for the crossbeam. And they are light enough to carry to where the work is. The beam also has a convenient carrying handle.
Height is a consideration that's often overlooked.
Most sawhorses give you a working height of 24 to 27 in. This is a comfortable sawing height for most people. For instance, when you use a power miter box, a taller horse will make it easier to see your cuts without straining your back. Adjustable legs are also a big plus when you're working on uneven surfaces. Another way to raise the working height of a legs-only model is to use a wider crossbeam, like a 2510.