Not a fan of bleed valves, if you have your bonnet open people can fiddle with it and turn it up to a stupid level ( you might get tempted to do it yourself You can still fiddle with a digital one, but at least you can password protect it. Also digital has a finer control boost which means you could get closer to the boost threshhold of your components without expensive engine parts ending up on the road in your rear view mirror If you're going to set it to a sensible margin and are happy to leave a margin in for boost fluctuations and you know no one will play with it, go for a bleed valve as they're only £30, if you're going to keep playing with it and have maybe a couple of different boost settings, go digital.