Coils come with their own, not insignificant problems. For one thing, coil spring setups tend to be heavier than leaf spring setups. Leaves, in themselves, are heavier than coils. BUT to use coils, you need links, and those add up the weight very, very, quickly. Coil systems are bulkier as well, and they are very "tall". Leaf setups are not tall at all, and can be packaged with much more ease. The forces on a frame with a leaf spring setup is much lower. Coil setups tend to load a frame from one point as opposed to two per side on a leaf setup, plus coil setups also introduce twist in the chassis rails. Add to that fact that coil spring setups, especially repurposed ones, are very difficult to setup properly as well. You can end up with all manners of odd U-joint binding and steering binding issues. With leaves, the motion arcs are much better understood and generic.
That being said, with coils, you've got much more freedom to play around with different parameters, so for some, that is a definite plus. As an example, the JJ crew prefers coils exactly due to the freedom of design provided, while the UZi crew has achieved quite a remarkable amount of travel from their reverse-shackle leaf setup. In fact, for a Vigo, I would recommend something like UZi's setup rather than a coil-sprung four-link if you're not willing to do 20"+ of travel. By my calculations, you should be able to get an easy 14"-16" out of a set of long leaves and reversed shackles.
