There's nothing glaringly different between the two, other than the VPN route showing fewer hops (although it won't be showing the hops to the VPN server, I think) - the overall latency is roughly similar.
The only thing I can think is, as @wkirkman suggested previously, one of the routers on the non-VPN route is overloaded, or has a dodgy connection, and is dropping packets (packet loss requires re-transmissions, which reduces the overall throughput of the connection).
Unfortunately, there's not a lot you will be able to do about this. It's quite possible that the problematic router belongs to a non-BT network operator, so complaining to BT is unlikely to have any effect. The only real hope is that the operator in question notices the problem and fixes it.
In the meantime I think your best option is to keep using the VPN.
