I've got the LE, which doesn't have digital outs, but it does have balanced analog outs, and that's what I use -- I just set the Tonelab for "line" output (as opposed to "amp"), run TRS cables from the L and R outputs and put them into two line-ins (*not* preamps) on my audio interface, then assign those two inputs to a stereo track in my software.
Theoretically, S/PDIF could be a little better, because you would skip one D/A conversion and one A/D conversion, but you'd have to figure out how to get it into your computer. If you're going in through an interface, you may have to set the interface to use the "S/PDIF" clock source (and hope it works) to avoid yucky clicks/pop/static that can occur when two digital devices are out of step with one another. It doesn't *look* like you can cause the LE to use an external clock source, whether it be from the S/PDIF connection or otherwise, so it'll be up to the connected device to groove with the LE, if it turns out to be necessary.
But I'd just try the analog line method I mentioned (I think the LE has analog outs, right?) or even micing your amp if you like the sound that's coming out of it, before I ran out and bought anything to make S/PDIF work. If do decide to go that way, best of luck to you -- I have several converters that have to work together, and it took me forever to get them all grooving on the same clock signal.
