Is the current 870 Express only cosmetically different than an 870 Wingmaster?
Yes and then some. There are even differences between the older Expresses and the newer one. Functionally perhaps some minor diffferences. You can make the measure on these. Cosmetically; Major differences. I'll list just a few on the newest Express.
1. Weaker magazine springs that readily lose their memory.
2. Hulls stuck in chamber and won't extract.
3. Not just a dull finish but a deeply grooved finish that lends itself to rusting, More readily. Take a new one, wipe it down and see what you get.
4. New ones only come with a Modified installed choke, older ones had three.
5. New ones have little or no wood protective finish, mostly a stain. One good season and it's gone. I've seen them come out of thhe rack, all scratched up.
6. Stocks are laminated birch as oppose to solid birch. Actually, I don't mind this.
7. Trigger group housing is now synthetic/plastic as opposed to metal.
Yes, the new Express is still a good functional shotgun but again. you get what you pay for. I'm very happy with my "Older" Express and more so with my Wingmaster. ...
Be Safe !!!