Coming off a cruise ship for 1 day in St Kitts next month.
Question - for the 1 day, which is better from a tourist point of view, St Kitts or Nevis for the day? Would appreciate in addition to your answer, sights to see/things to do there?
thanks!

One is not better than the other - they are just different islands - sort of like asking what's better vanilla or chocolate ice cream. Each island has its own appeal.

You need to supply more info:

How much actual time will you have in port?
Regardless of the island, will you be taking a "ship sponsored" excursion, going on an independent group tour, hiring a local taxi for a private guided tour or are you planning on doing a self-guided tour in a rental car?

If going to Nevis on your own were you planning to take passenger ferry, car ferry or private water taxi? Also, what mode of transpiration were you considering once on Nevis?

Answers to above questions will determine which island to recommend. Keep in mind when considering visit to Nevis that depending on the mode of transportation you choose to get there you'll "lose" anywhere between 1 1/2 to 2 hours making the crossing back/forth between islands. Also ferry schedules may not "mesh" all that well with your ship's arrival and departure times which could further limit your available time on Nevis.

As for what to see/do on each island a simple internet search for "Things to Do on NAME OF ISLAND" will bring up lots of links.

I think you'd be hard pressed to make ample time for Nevis with just 1-day. Not to say it can't be done, but there's plenty to see and experience on St. Kitts and you'd lose a lot of time traveling, as mentioned above, to get to/from Nevis.

Nycgirl1: since the cruise was this month, my guess is the decision was made weeks ago.

wow. that was a bit of an unnecessarily snarky response - a lot of people use these to research for years on end, even if it doesn't help the OP (which clearly I missed.)

>>a lot of people use these to research<<

Yes they do. I was trying to help since you were obviously trying to help the OP. My response wasn't snarky -- my guess is their decision was made weeks ago.