They have the same ratios - I would purchase from Niagara because I have had good luck with them.

If you need the 28T for where you ride, go for it. My rides are very flat, the toughest challenge being an overpass, so on my World Tourist I have a Sunrace 13-25T 7 speed freewheel: 13-15-17-19-21-23-25; and I plan to eventually get a IRD FW772 13-14-15-17-19-21-24 which has better ratio spacing. On my Sierra Sport; I have DNP EPOCH HYPERFLO 7 Spd Cassette 13,14,15,17,19,21,23T - which I like a great deal. My Miyata will be getting a Sunrace 13-25T 7 speed freewheel: 13-15-17-19-21-23-25; as I have a second new one.

If I had any hills to tackle, I would go for the wider ratios, but on the level having close ratios around your cruising speed is really nice.