And if you're interested that's the same weight limit for a short-wheel-base Transit van, but if you wanted to send a long parcel then their are differences in the length of parcel you can send.
The SWB has a limit of 1.6m for any one item, whilst the LWB has a limit of 2.5m for any particular item.
Depending on where the parcels or items are being collected to and from their may not be a massive difference in price. A same day delivery of an item under 1000kg from Manchester to London, perhaps the Premiership trophy going from Old Trafford to The Emirates Stadium (it'll never happen) would cost £263.27+vat for a SWB and £284.33+vat for a LWB. For a trophy that might seem excessive, but for some machinery, much-loved furniture or exhibition stands it may be just what you needed.
And if legal documents were ever going to go from Arsenal to Chelsea FC then it would cost just £9.62+vat by motorcycle or £12.50+vat by a small van (500kg weight limit, max length 1.2m).