Is this a good deal on a suit?

I own multiple Suitsupply suits (including a Napoli) and find them really good, so I tend to stick with that. No experience with Suitdepot, but the way they present their products make me think they might be of slightly lower quality (or they just spend less on marketing, which wouldn't be that surprising since Suitsupply tends to go hard on that side). As a general rule, go with the one that fits best (either in-person or through online measurements) as long as the color is all right.

Nevertheless, I would point out one thing: the fabric. You're talking super 110's vs. super 150's, which is a rather significant difference. The fabric issue represents a basic trade-off:

Low number: Low thread count per square inch/cm => larger, more robust threads

• Not as soft as a 150's
• Better durability

High number: high thread count per square inch/cm => thinner, more fragile threads

• Softer than a 110's
• Poorer durability

The key point here would be how often you would use the suit. If it's part of a, say, 5+ suit rotation with about one day of wear per week, then it makes sense to go for a 150's. If it's still part of a "basic" rotation, I would go for durability. Of course, that's assuming all else (e.g. overall design, fit, pairing options) remains equal.