I'd say it was quicker from LR. Come out of on the Brighton-bound side by the Signalman, walk down Ditchling Rise and go straight across Beaconsfield road into Argyle St. It's on your left.
It's fine if you get the 13:55 from London Road, its usually an 8 carriage train. Go in the front carriage and you get it more or less to yourself. And at this time of year you can pick blackberries on the platform while you wait.
Oh wow can you really?, a year later and it must be nearly blackberry picking time again.