The point about getting a 2-wheel roller instead of a 4-wheel spinner is a good one, but the last time I shopped for luggage, I found it harder to find a roller; spinners are much more popular.
Spinners are fine for smooth, flat surfaces, and for most people, whose bags go from car to airport terminal to hotel and back, no problems.
They're not so great for going over rough, uneven surfaces, like old cobblestone walks and pavement, if you're dragging it to a private rental after being dropped off by a cab, or taking public transit.
But if that's the option taken, at least choose one that has wider single wheels, not tiny dualies in each corner. Tipped at an angle, and resting on only two wheels, a spinner with the larger wheels can traverse terrain ok.
My impression is that European carriers have tighter luggage requirements, but in any case, it's best to do your homework beforehand.
I can't say how the airlines approach it, but luggage dimensions are nominal anyway, at least from the makers. And those classifications have wiggle room in themselves, with 27/28/29/30" options, depending on who's making it. One "27-inch" bag is not going to measure out exactly like one from another brand.
Going further, I compared two 27" bags last time, one that was slightly wider, but shallower, and one narrower, but deeper, which I found to be more practical.
Oh, and packing cubes are great at maximizing the available space, and organization helps keep things from becoming one pile of clothes mixed up in a box.
If this is going to be a repeated exercise, it does make more sense to buy a nicer bag, with a better warranty that the manufacturer is actually willing to do repairs on. A leisure/occasional traveller? Might not be worth the money, since it won't be used as often. The luggage handlers and system don't discriminate, and will beat them both up anyway, so a more moderately priced (but not dirt cheap disposable) is less likely to cause agita when it gets damaged.
Like many product categories, there are only a handful of manufacturers behind the major brands anyway, and it's a big exercise in marketing segmentation for what are fundamentally the same components, with certain niceities added to justify each jump in price or prestige. A lot of that extra coin is going to the warranty and service support, so it's not unlike buying a commodity-like car battery.
On a longer trip, with few or no connections, I'd be checking the bag anyway, and not worry about overhead dimensions, just weight. A bathroom scale alone, or with you as tare will help get you in the ballpark without having to buy more gadgets.
With KLM, signing up for their frequent flier program for free waived the bag fee, at least a few years ago.