It could mean nothing. It could mean something. Meaning that it could just be marketing and packaging the same tape. Or it could be the pro-level tape has gone thru some more Q/C processes and higher standards for reliablity, etc. perhaps it is drawn from th emiddle of the original spool, where the tape is the best, maybe it has a slightly thicker magnetic coating, etc. We can't really know, unless someone has a reliable document to prove one is better than another on a scientific basis.
Considering tape is the cheapest thing we buy, except when it has failed, I don't think it's worth quibbling over an extra buck or two to get something that works for you. If you get massive dropouts on an irreplaceable tape, the client is not going to care that you saved two dollars over the high grade stuff.
Pick a supplier, test it out a while, then stick with the one brand.
I agree with Mark. Unlike analog, you may not see the difference in first generation picture quality but higher grade tapes do have higher coercivity and retentivity, which makes them better at attracting and retaining magnetic signals and less likely to have dropout. They also have a greater particle density and higher grade mechanisms. The professional grade products are subject to higher quality control and frequently come from a more consistent part of the pancake. Depending on your budget and the amount of footage, a couple of extra bucks to 10-12 bucks a tape may be gilding the lily or it may be the difference between a successful shoot and a failed one.