I've been trying to find out what specific differences there are tween The Last Express and the Gold Edition. Differences other than what is said at Steam. I just now learned that the GOG version is the original and the Gold Edition has been altered for mobile and "i" devices. The article said that they felt the quality is better with the GOG version.
I just bought it from GOG...and it's a dollar cheaper.

ETA: I read the article at http://www.shotgaming.com
Tagged Steam Shots.

I think the steam version is basically the smartphone/tablet version on a computer.

Yes, It took me quite awhile to find out any info. Most of the googled sites I found quoted steam's differences which didn't give me my answer.

i have played both the versions but i found the gold edition to offer a better chance of completing the game , the hint system was needed for this game and game is bit better accessible hope gog gets the gold version soon