I purchased this along with the SD70 Vol2 dlc pack to round out my BN/SF stable. I like that there are variants for both Santa Fe and post merger lettering.
Soundwise these locos are identical to the SD70's, so nothing new there. If you like the sounds of the SD70, then you'll like the SD75.
Along with the war bonnet paint scheme there are some minor differences inside the cab. It actually "feels" a bit more cramped inside the SD75 than the SD 70.
Like the SD70's, the headlights don't work very well. They turn on, but do not cast any real light ahead of the loco, so night time scenarios are rather pointless. Aside from that, it's a decent loco that will add a bit of history to your BN/SF stable.
The locos do look good, and are a joy to drive. If there were a star rating system, I'd give it four stars.