Based on my experience in extraction, from a chemical engineering perspective, the smaller the “tank” the better as long as there is sufficient room for print movement. Several changes of water in a small tray or tank or whatever is theoretically superior to either constantly moving or large stagnant quantities for removing small concentrations of whatever, in this case fixer et c.
It makes sense when one considers the concentrations involved. Final washing involves a lot of pseudo-diffusion where molecules of hypo et al. migrate slowly through paper fibers and emulsion layers into a less concentrated solution – wash water. In the case of fiber paper, there is a lot of hypo that is attached to print materials in a loosely chemical bonding called mordent. This is similar to the “bonding” of some dyes in cloth. Normal diffusion mechanisms do not apply in this case and the washing is more or less at a constant rate – whether the water is moving or not.
As others have mentioned, I also use a modified siphon technique, filling and emptying about a pint per minute for an hour (after all the preliminary prep with HCA et c.) I guarantee my framed prints against all damage from “normal” aging and so far, except for one delaminating print due to a cleanliness error during mounting, there have been zero complaints. (Now said, watch the complaints come rolling in!)
Thorough washing is very important. If you have doubts as to the effectiveness, wash again, and always use a HCA.