I agree with the previous posts. One thing to keep in mind is you might also look into making it handicapped accessible if the building is as well. It would be an attractive item for more potential buyers. Think wide doors, low/zero thresholds, quality tile work with appropriate fixtures. Where it had a full tub in there already you really have the option of making a nice large shower. Splurge on a higher quality tile job that will stay current longer & appeal to a larger group of potential buyers if resale is a concern.
Have you consider keeping the tub bring that entire area "fashion forward" with tile , design and etc. Therefore whenever you sale home you have larger buyer group than just a shower.
Personally I hate tubes I believe they are waste of space... LOL... however many buyers like tubs or if they have children kids can soak in their bath, and master will have their tub.
Many buyers are picky... ANOTHER EXAMPLE I have a buyer who refuses to purchase a home without a fireplace has PASSED UP HOMES WITH EQUITY over 40% I had contractors speak with her, how to convert a home include fireplace. LOST sales for these homes on market
Hope that assists