eBags
 

Picked up an eBags EXO Hardside 24" Spinner not too long ago. I'm personally biased to hardside luggage when I travel international and have become totally spoiled by 4-wheel spinners to the point where my 2-wheel luggage almost never hits the road any more. As pointed out previously, packing for a month-long trip and not planning to do some laundry is not the most realistic scenario - how many people own that many sets of underwear and pairs of socks; and do you want to fill your suitcase with just socks and underwear? The big difference in space between the 25" and 28 or 30" is usually caused by the depth of the case. We took the 24" out for a 1-week test trip and it held a boatload of stuff - jackets, summer/winter (don't you hate when you have to pack for both?), full-business, biz casual and just for fun. As mentioned previously, they seem more concerned with the weight, more so on international than domestic (which I've rarely seen them weigh), than size, but all it takes is one stickler for the rules and your 1" oversize can cost you the big bucks. Same goes for the weight.

I may not be the best person to give packing large advice, because I've been known to go on 2-week cruises with just carry-on luggage (yes, I jammed those formals and the shoes to go with them in there along with every electronic device known to man and everything else).

You want a normally packed bag to be under 50LB. That really depends on what you would be packing: if all fluffy sweaters, even 31" might be fine; if mostly books, chocolates, wine bottles, nuts, china and crystals, even 25" might prove too big. :)

If mainly clothes, you can probably go with 28". However, books and gifts have a way of sneaking up on a traveler's plans and for myself I feel safer with 24"-26".

In luggage matters, it is a wise idea to listen to Till (tfar). Try out a few size(s); only you can do it for your requirements. Once you discover the size that fits your needs, you can get a lot of information here on brands, warranties, value.

Only you can decide if it's too small for your packing needs. Personally I don't own a 28" bag. I did a month in the UK with a 25" bag and my wheeled laptop case. I did laundry twice, about every 10-12 days so I got a fair amount of clothes in the 25". A 28" bag can very easily get overpacked and exceed the 50 pound rule and to me it is a little unwieldy. I would buy the 25 or 26 inch, do a couple of practice packs and decide from there. On another note I am returning to the UK in the summer and everything is going into a carryon and a tote. I don't check bags anymore unless I am packing my hiking gear. Security does not like my collapsible Leki trekking poles in my carryon.