I take issue with the question as well as most of the answers.
Firstly, the translation of the Italian is wrong. Confondere means "to confuse" and closely resembles the synonymous English word "confound". In fact, the origin of both these words lies in the Latin "confundere". Not only that, but 'con' means 'with' though the distinction may not be meaningful here.
So the example actually translates as:
Joe: "LaTeX è come Word" (LaTeX is like Word)
Carla: "Per piacere, non confondiamo l'oro con la tolla!" (Please, don't confuse gold with tin!)
As for an idiomatic parallel in English, the above answers really aren't satisfactory. As a matter of opinion, I think that Shakespeare probably best captures the crux of the above Italian idiom in his famous line, "All that glitters is not gold." 'Glitter' is obviously used metaphorically. Advanced LaTeX usage usually requires compilation steps that are far more difficult than just using plain Word. What this metaphor would mean is roughly 'Not every word processor is of the same caliber.' Note that in your question it isn't clear which option is tin and which option is gold. This holds true here as well.
Joe: "LaTeX is like Word"
Carla: "All that glitters is not gold."
Above, Carla's meaning is implied from context which option is the inferior one. A slightly more contemporary alternative would be to refer to the inferior option as "Fool's gold."
Joe: "LaTeX is like Word"
Carla: "LaTeX is fool's gold."
If we want to venture away from heavy metals, the best idiom that establishes hierarchy of the two options is:
Joe: "LaTeX is like Word"
Carla: "Please, you don't know which side your bread is buttered."
Note that no matter what expression you choose, as well as the original translation, all imply a deficit in the logic of the person who delivers the unlike comparison. There is no way to escape a negative connotation. Even if 'confondiamo' meant compare (which it doesn't), there would still be a context that implies a deficit in reason.