Two wheels vs 4 wheel spinner bag

I would recommend the even more traditional convertible carry-on with back pack straps.

Best number of wheels on any pack: zero.

Four wheel spinner - most definitely

Just don't buy anything larger than carry on size - and check the weight of the bag when empty. Remember, even if the bag is on wheels, you have to lift it on and off trains, up stairs to the train and in your hotel, and place it in the overhead space on trains, on the airplane. I prefer 2 wheels, larger wheels are better than the 4 tiny wheels. You will mostly be pulling the bag behind you, so the larger wheels work better on uneven surfaces. The small wheels can get stuck in cracks in cobblestone streets. Finally, YOU get to decide which you like better, but think about the weight of the bag first and buy the lightest you can find no matter if it's 2 or 4 wheels. We've been to Italy over 10 times now, and done it with backpacks, convertible luggage and wheeled luggage. For our needs now, we like the wheeled carry on size. Just so much easier on the back, shoulders and for walking. No matter what, to me, it's a total pain to wheel your luggage while walking to a hotel, it's just not a fun thing to do...but I'd rather WHEEL it than carry it now...

I prefer two-wheeled carry-on suitcases too. The wider apart the wheels are set, the less chance the bag will flip over as you're pulling it. I bought my current bag 4 years ago and have taken it to Paris, London, Germany, Luxembourg, and Amsterdam. Had to hoof it down and up stairs in train stations and up and down stairs in hotels, but that's par for the course.

As a backpack person, there are 4-wheel bags with wide-set wheels that increase stability; some of the first generation bags weren't so great. Also, be sure you can also tilt and pull it, like you would with a 2-wheel bag. You'll need to quickly get it up and down very narrow and steep train steps, so watch the weight - you'll need to hold it up in front of your waist, or throw it up or down ahead of you...but an Italian train station isn't a place where I let my bag get out of my hand :-( You'll also be carrying it quite a bit - up and down stairs, escalators, over thresholds - so be sure the handle is sturdy and comfortable, packed.

I've done the backpack. I've done the 2 wheels. Now I have a 4 wheel Lipault spinner. I find it much more user-friendly than anything else. The tip about not letting any bag out of your hands is a good one. It sounds goofy, but I got a slip lead, like they use on dogs at the groomer or the Humane Society. It's plenty long enough to attach to the top handle of my bag and around my hand as I roll it along and if I stop for some reason like maybe a gelato while on my way, I don't have to leave the bag just sitting there. Someone would have a very hard time getting the thing unattached from me and it wouldn't be worth the effort.

While I too would vote for no wheels for my carry-on, using the RS convertible with shoulder straps, if you also need a checked bag, wheels are handy provided that it can also be easily lifted. Many of the places we experienced in Europe are not mobility impaired friendly. I.e. bridges in Venice with steps, hotels with no lifts, and cobble stone walks. With cobblestone paths/streets in mind, rolling bags with robust inline skate type wheels like those on my LLBean rolling duffel gear bag are a plus. It also helps if the bag can be half lifted while rolling like my ski bag, so that the loading of the wheels can be reduced while on the cobbles.

You might want to review last week's discussion on same subject at https://www.ricksteves.com/graffiti/helpline/index.cfm/rurl/topic/105286/spinner-wheels.html

I realize that not all 2-wheelers have inline-skate-type wheels. I was merely reporting what I saw. I think even my RS 22" 2-wheeler that I've had for years has better wheels than I saw on the spinners at TJ Maxx and Ross last night. Apart from the wheels, there were some nice-looking bags that seemed to be good quality, though I didn't spend much time looking at them in detail.

I have used my two wheeler carry-on in Italy (hill towns, Venice and Rome). It works well because it has larger wheels. Would not use my spinner in Italy unless I was staying in one place. Beware stations - they always seem to require climbing stairs and neither wheeled sort of case works well in that situation.

I don't know where y'all are buying your four wheel spinners with tiny wheels. The wheels on my spinner are the SAME size as the wheels on my two wheeled luggage and with the same wheel base. My spinner is only a year old. I think of it as my old 2-wheeled luggage on steroids, twice as easy to maneuver.
I think tiny wheels are an urban myth. I'm off to TJ Maxx and Marshalls to do some research.

I looked at spinners at TJ Maxx and Ross last night, only out of curiosity because of recent discussion about it here and because I don't need anymore luggage. The wheels on all the spinner bags I saw in both shops are smaller than the industrial-strength inline-skate wheels on the Osprey 2-wheeler I bought recently.

BUT not all two wheelers are Osprey with industrial-strength inline-skate wheels.

Elaine, the first spinners had tiny wheels; the newer ones have larger wheels, AND can be tilted and dragged like a two-wheel bag (some have two larger wheels in back...). Those were good ONLY for smooth sidewalks :-( Many peeps would replace their (always-falling-off) tiny wheels with larger ones, anyway, so the smart manufacturers took note and got on that bandwagon.

A few years ago I went around Italy with a 24" RS bag with shoulder straps, and carried along a lightweight luggage tote (the kind you secure with a bungee type cord) for when I did have to go distances. I found that most airports have luggage carts you can rent or use, and I did use those, but I could also carry it on my back for a few blocks. I just got back from doing train travel in Scandinavia, and what everyone says is correct: the ones with wheels are MUCH heavier (ca. 10 lb), but that's what I used. It was awful to try to get it lifted up onto the trains, over and over, although there are places at the ends of coaches where you can leave luggage too big to go overhead, and that's what I used. Thank heavens for nice big Nordic types who helped me! My bag was much bigger than almost anyone else's on the train, too.