Sometimes with the centre mounted jockey the tube can get jammed in the hole in the A frame and as it is fully enclosed it can - to use the previous quote - be a pig to release as the clamping mechanisim is inaccessible and does not always release the tube. If there is some weight still on the jockey wheel you have to lower the steadies to relieve the weight and then free the jockey wheel. A side mounted jockey wheel although not so pretty is far more 'servicable' and far easier to remove if required - you can see what you are doing!
At one time (on a previous van with side mounted jockey) I used to remove the jockey wheel completely to reduce nose weight - it was an easy operation with side mounted jockey, but it would be a right pain with the centre mounted as you would have to separate the 2 halves of the jockey wheel, lift the top half out of the A frame from the top and lower the bottom half from underneath and risk getting black grease everywhere. Also it is more awkward to align the slots in the outer tube with the wheel supports.
Nice to look at, but not very practical.