They are both exactly the same as far as power, but it's the type of stimulation they provide that makes them different. Salsa provides a more pinpoint stimulation, where Tango provides a broad stimulation.
The We-Vibe site specifically states that the two are identical (in power, length, charge time, etc), aside from their tips and their color options. The Salsa has a point and comes in black, red, and black, while the Tango has a lipstick tip and comes in blue, purple, and pink.
I personally think that We-Vibe was trying to appeal to male-bodied people that enjoy bullet vibes with the Salsa, given the shape and colors, with the Tango being the traditional female offering. Salsa's discontinuation is due to the Tango selling better/We-Vibe streamlining their product line, not to the product itself, so you're getting a nice, rumbly vibe either way.