I really depends on what your journey preferences are. If you wish to look at the scenery, then the A701 does give you that. If you wish to get to Edinburgh quicker then staying on the M74 a bit longer to Junction 13 and taking the A701 will be the better route, From Junction 13 it is about 1 hour, with a caravan, to Edinburgh. The A701 also runs parallel to the A 702 for a lot of its way, so 6 of one, half a dozen of the other. Neither road really has a high traffic density, unless you are stuck behind a slow moving vehicle, which can be fun. Both the A701 and the A 702 hit Edinburgh's bypass at adjacent junctions. Straiton for the 701, Lothianburn for the 702. These 2 junctions 'straddle Mortonhall carvan site (peaceful and attractive). If you wish to use the CC site at Silverknowes then you need to travel round the city to get to the northside alongside the Forth estuary. You can drive throught he city, but like many others, it can be fraught at the various junctions, and the one way system really needs to be known in advance. Just try to avoid the bypass at the morning or afternoon rushours, it is becoming more and more like the M25 every day.