For 99% of shooters there is no difference from a function point of view. A 85 Combat with competition fixed sights will shoot with the Shadow as the guns are essentially the same gun, The Shadow has a slightly different frame and the FLDC. The hammer/trigger has been worked pn to improve the pull and that is about it. Is the extra money for the Shadow worth it. If you prefer the feel of the Shadow, think the FLDC is cool and understand the 85 Comabt has a slide release lever that can and does fail from time to time then the extra dollars are worth it. If you prefer adjustable sights on your gun, like the full ambi nature of the Combat and want to save the money difference and apply it to ammo then the Comabt works for you.
I have the 75 B Shadowline along with a couple of Combats. One of the Combats has had trigger work done on it and the gun has a far better trigger then either my 75 B Shadowline or any stock Shadow out of the box. The other two are pretty much stock and don;t have the trigger of a stock Shadow out of the box. I prefer the looks of the regular dust cover and know the FLDC would have no affect on how I score when shooting. Some would see an improvement in their scores, most would think they would.
Be realistic and think about what you intend to do with the gun. Both work well and are excellent guns. The Shadow out of the box is set up for IPSC Production and IDPA SSP Division. The 85 Combat will serve most new shooters equally as they will not likely have the skills to take advantage of the lighter SA trigger pull. The Competition sights on the Shadow I think are better sights for most shooters whether they play the games or not. If you are new to shooting you likely will benefit more from the extra $200 worth of ammunition you could buy then you will from the few features one gun has over the other.
All that said, the Shadow is a very nice piece of kit that will last you a life time. It is a very good buy if you want a SA/DA pistol.
Take Care
Bob