Looks like you beat me to it, Simulatortrain, including the part about calling it a BP20 being the wrong thing to do.
In any case, to expand upon what he said, Baldwins are particularly difficult to identify at times, especially the switcher models. External differences can appear on even the same model of locomotives. The names, as was pointed out, refer to the internal components, rather than the external shell, which tended to be more of a one size fits all type of thing.
In fact, the 6 axle passenger Sharknose, the CNJ double cabbed Babyface, and the regular 6 axle Babyface were all the same locomotive, just with different body styles. (the CNJ units being a slight exception due to the double cab)
The difference between a VO and a DS/DRS/DT is that the VO models had a turbocharged VO prime mover, where as the D models had a NA non-turbocharged prime mover. VO's also did not refer to their role or axle count in their name, just VO and their horsepower. The D models referred to their prime mover, role, axle count, powered axle count, and horsepower. Later on, Baldwin tried to simplify this by creating the AS(all service), RS, RF(road freight) and S classes, though it was already getting to the end of Baldwin at this point.
The reason for their odd naming scheme is also the reason for their demise. Baldwin never adapted properly from steam to diesel and applied steam locomotive practices to building diesels. One of these was allowing railroads to customize their orders like they would with steam engines. This was costly, and hardly efficient.
As for the original question about the difference between a DR-4 shark and a RF-16 shark in regards to external features there really aren't any. The DR-4-4-1500s had some issues when they were first introduced, and came in babyface and sharknose. Once the bugs were worked out it was rereleased as the RF-16 and only came in Sharknose. This was to fully promote it as the sharknose and get away from the stylings of its competitors, as well as to move away from the memories of the DR-4-4-15's teething issues.
