I am really enjoying the 28 ga! And my wife is loving it too!
But I pretty much am just using it for ruffies and blues.
Hope to get a chance to use it on Huns and chukar at some point.
Also hope to try pheasant hunting someday, but am looking at the Fiocchi Golden Pheasant loads mentioned above for that (or the possibility of getting the Benelli Ethos which has the capability of using 3" shells for the extra punch; but since this will only happen in conjunction with the odd antelope hunt in southeastern Alberta, is not high on the ranking of priority, but just a thought of versatility for those special occasions).
I am currently waiting for COVID to end so that I can get a price and availability on an Ithaca M37 w/ straight stock in AA grade wood, with 26" barrel in 28 ga, and make my final decision on it, a Benelli Ultralight or the Ethos for my next shotgun, as the wife has claimed my Remington 1100 Sporting 28. I also have a Cooey 84 and a Winchester 37A in 28 ga for myself and my daughter to pack along on big game hunts for the ruffies.
I do like the 20 ga (and actually preferred it on the sporting clays range the few times I have gone, over the 12 ga's I tried, but mostly had more to do with the firearms that were neutrally cast and made my left handed shooting more accurate), but as I do not hunt waterfowl, haven't seen the need for more power than what the 28 provides me on the uplands birds I am hunting normally.
As for costs of shells, this is typically the cheapest expense of any day in the field or on the range, and is just part of the adventure, so I do not normally factor that into my decisions. We spend hundreds to thousands on firearms, and hundreds to thousands on hunts; a few dollars extra for the ammunition, regardless of gauge or caliber is moot. And the projectiles are the component doing the actual work on the targets, whether they be game or clays, so I have often wondered why this is such factor for most people who are not shooting thousands of rounds a year?