In many ways there isn't a lot to say here. Century: Spice Road and Golem Edition are essentially the same game. The cards are the same in the sense that they do the exact same thing. So, what are the differences?
The biggest difference comes not in the game box itself, rather in the plans for the future of the series. Spice Road is part of a planned trilogy of games that work together in some way. This trilogy is not currently planned in Golem format. It's not even mentioned on the box.
But then again, Plan B Games said that the Golem Edition would not be released and then released it, but not to retail, saying it wouldn't come to retail, then it came to retail. This doesn't seem to be a case of a company flip flopping, as the customer demand for the Golem Edition was palpable. So, if there were such a demand for the Golem trilogy...
Century: Eastern Wonders is the next in the Spice Road trilogy, adding pick up and deliver mechanics and a modular board. You can play the game in a number of ways and include the cards from Spice Road. You want this for Golem? Then go tell Plan B Games!
100 Year War
Other than that, there are slight component differences. The most striking is the incredible artwork in the Golem Edition. The art in Spice Road is perfectly serviceable but is just a little bland in comparison. Golem Edition is also way more colourful in terms of card backs and the crystals look better than the cubes in Spice Road.
Personally, I prefer the four shaped bowls in the Golem Edition as they are deeper and fit the crystals in more comfortably than the standard shaped bowls fit the cubes of Spice Road. The coins are the same apart from a slight colour difference.
The big one for me is the insert. In Spice Road the insert is not as deep as it could be and even struggles to fit the cards in flush after a good shuffle. Golem Edition, however, is better thought out with plenty of space and a clear plastic lid to cover the bowls and crystals keeping them in place.
50 Years of One, and Half a Century of the Other
So, which should you get? Well if you are remotely interested in the Spice Trilogy then currently the only certain way to go is the more standard trading theme. However, if you aren't interested in the upcoming games, or you feel patient you could great the much prettier Golem Edition or just wait and see what happens.