Tuning SU's is pretty darn simple. As long as they aren't worn to bits there is a simple little procedure to go through that is pretty cut and dry as to which way to nudge the mixture. Then there is the slight black science of picking the right needles (if your engine isn't stock) but they are cheap, and guys like Rhys can make suggestions that are usually right on the money.

Balancing them can be a bit trickier, and necessary only if you want that silky smooth idle. But it's not that hard - especially if you have a carb balancing tool.

The DGV/DGAV carb is adaptable, but tuning it (like most other Webers I know about) involves swapping little fuel jets, emulsifier tubes, and air corrector jets. Not just turning an adjuster a few flats like on an SU. IPD used to (and probably still does) rent out a small case full of jets, and to get a proper tune you had to spend some time on a dyno, swapping jets and checking the results.

And when said and done, the DGV/DGAV is barely adequate for a bone stock engine, if you ever try to increase the output of your Volvo engine you'll hit a qall quickly with that carb and manifold setup. The overall flow rates, the awkward manifold runner layout will be the main bottleneck. The SU's and their more direct manifolds will keep up with motor improvements longer, with a cheap needle change possibly needed.

Now the dual DCOE webers are doubly complicated in terms of tuning as compared to the DGV. But at least in their case you get something in return - a more grunt (especially with some engine mods) and a razor sharp throttle response.
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I'm JohnMc, and I approved this message.