I'd go with the navy ludlow in Italian wool, double vented with the slim pants if I had to choose only one for year-round wear. I have the Italian wool, worsted wool, cotton piqué and linen, all in navy, and I find the Italian wool the most versatile. You can dress them up, dress them down, and wear them as separates. Not too heavy, not too light, easy to maintain.
I recently made this decision. I have a wedding to go to at the end of this month, and used it as an excuse to spend a bunch of money on my first suit. I really considered a Ludlow, but decided i'd check out SuitSupply since there was one newly opening near me in Atlanta. The Ludlow has that lower button stance which is really flattering, and it was really nice to wear. When i saw the Napoli light grey and put it on i was sold right there. The staff at SuitSupply were awesome, and i even got to go to the opening night party, though that story is longer. Anyway i can't say enough good things about SuitSupply really. If it has to be a Ludlow though?
The Napoli in Navy is very dark, I think Navy is preferred as in low light situations it's dark, but in high light it has a slight blue to it. Men look best in blue is the general consensus and darker colours will make lighter skin tones look washed out and lifeless. I personally dislike my charcoal suits compared to navy & grey.