What's under the floor? Tongue and groove, with a bead of adhesive along the groove, becomes a moisture barrier. That's good if you're above a crawl space or other area with moisture. Tongue and groove also supports more weight along the seams. Finally, tongue and groove won't grind its edges into sawdust over the years, opening gaps in the seams and causing noises. So you have to decide if these things are important to you.