Lowden Guitars have always been strong advocates of the pin-less bridge and George himself responded to the question of its advantages/disadvantages in a Lowden news group with the response below. Hope this helps.
Regarding the design advantages / disadvantages of my pin-less bridge:
As David has said, the main downside could be that a pin-less bridge will come off more easily than a pin bridge. But it is very important to realise that given the same climatic conditions a pin bridge will also lift off the soundboard at the back, the difference would be that a pin-less bridge is likely to separate completely or nearly so, ..... The way a pin bridge behaves under these same circumstances is obviously less dramatic - but must nevertheless be repaired the same way. Rarely does a bridge come off if the bridge is kept from drying out too much, so be very careful to humidify the guitar in dry periods - particularly if snow is on the ground, and central heating is on.
The main advantages of a pin-less bridge are to do with the tone characteristics. Because the rake angle taken by the strings over our saddles is shallower than on a pin bridge, I am not so restricted by structural considerations with the bracing / bridge interface. The bracing can then be designed in such a way that it encourages a lot of relatively complex oscillation modes, which in turn helps to give the Lowden its particular tone.
All experienced guitar makers know that creating unplanned for stress or tension in an instrument is not good for tone. The most critical area of the guitar where tension should be avoided as much as possible is the bridge and its joint to the soundboard. Any stress in there is going to damp and restrict the guitar's tone, volume and
sustain. A pin-less bridge will be an 'easier' fit to the soundboard, provided it has been fitted expertly.
This is a complex subject of course and so maybe someday I'll write a book about my ideas of guitar design and construction.... but then it might be too technical ..... I'd have to include some stories to liven it up a little! Maybe someday