A three-wheeled versus a four-wheeled stroller - which is better to fit my lifestyle?
TL;DR: Many parents are 'afraid' of a three-wheeled stroller - starting with the too "sporty" of a design, ending up being worried about the stability of such a model. Always be aware of better all-terrain driveability and spaciousness of a three-wheeler - and the need for such features for certain lifestyles (over the looks or the price). A four-wheeler might be - for its shorter base - better for less demanding (urban) conditions, general use, and foldability-wise.
When thinking about a pram, pushchair, buggy - any kind of a stroller model, the first picture in your head will most probably be going to have four wheels on its (imaginary) base. Why is it so? Well, the reasoning here would be historical, making us maybe a bit scared of the newer, three-wheeled, differently-looking design. (Did you know three-wheelers for sports use started their existence in around 1983, resulting in the Baby Jogger brand creation in 1984?) Another reason for the fright of the three-wheels might be those few cases of cheap strollers of a bad - not stable-enough design (that you or some friend had/or you read about being tipped over). In any case, both chassis types have their "hero" models and the "black sheeps" - and both their advantages and disadvantages, use-wise.
A four-wheel stroller is, as I said, a "traditional", classical, time-tested way of seeing strollers, and I have absolutely nothing against the general idea. Even if it, of course, varies from model to model, the stability is in general good, and the look feels symmetrical and, most of the time, stylish. The front axle's stability, the conventional design that can play it any way ranging from sleek/elegant to sporty (or rough-terrain robust), oval to square-ish, pretty to neutral... and it just works for most. That is why the majority of stroller brands go for mostly four-wheelers.. A four-wheeler is a go-to for you as well if no special requirements are in place, and the ride conditions will mostly be 'pleasant'.
On the contrary, a three-wheel stroller doesn't look elegant much. That is given by its longer and/or wider (in the back) design (stability increases so much with a longer and/or wider frame), "sharper" lines, often a decelerating handbrake on the handlebar, as well as usually larger wheels. When looking at a three-wheeler, you normally need something as maneuverable as it gets (valid even for those more urban three-wheeled 'buggies'), something spacious even for a very large child (a BJ City Elite can hold a 5-6yo easily), and something for getting over worse terrain (like on a dirt road or through the grass)... A three-wheeled chassis will just perform better if chosen properly - given it's a quality model.
Always look first at the front wheel - that is the first point of touching any kind of terrain/bump/hole/obstacle. It needs to be large and high-quality enough if you mean to get through uneven surfaces.
One thing I will not prompt you to buy, though, is a three-wheeled pushchair with a rather small (usually doubled) front wheel. And by tiny, I don't mean the Baby Jogger City Mini's front wheel - that is just fine for the size. Think more like Hauck City Neo-style - there, the three wheels do add on maneuv erability... Still, the stability and the front-wheel capability are somehow not good enough (or necessary) to be of this design.
Another thing to say about three-wheelers is that mostly, they feature non-reversible seat units. It's a good and a bad thing at the same time. It is a bad thing for those who need their baby to parent-face - but a good one from the point of space in the seat. A seat slung directly from a stroller frame means more width, more space for the backrest, and more space up to the canopy (that is also attached right on the chassis, not on any kind of seat frame that needs to be present with a reversible seat). I know how a reversible seat unit might seem like the only option at the age of around six months of the baby - but just a few months later, you'll see yourself it's maybe not worth a bulkier, less agile reversible-seat stroller model, and change it. Second-time mothers, therefore, often opt rather for a few months of "less comfort" with no reversibility knowing longevity-wise, a non-reversible seat is just incomparable (this is true for both 3w and 4w forward-facing, non-reversible models).
Of course, there are exceptions to the 'no reversibility on a three-wheeled strollers' rule
...like a [[bugaboo-runner|Bugaboo Runner]] or an [[emmaljunga-nxt-challenge|Emmaljunga NXT Challenge]]. However, a stable center of gravity not shifted by changing the direction of the seat when running or on harsh terrain is such an asset to have you might want to rethink the topic of reversible seats if planning to jog with your pushchair.
So when a four-wheel pram or pushchair?
Almost always, I must (unfortunately) say - because most moms are not into the design or simply don't see the added benefit of maneuverability through the negatives of a longer or bulkier chassis as well as the reversible seat. If you do mean your stroller to do mostly chores, usual everyday walks, getting to the playground or to the kindergarten, and shopping as well (= folding your stroller often), a four-wheel model will simply be easier to use.
And when to go for a three-wheeler?
Even if people think weirdly about a three-wheel stroller's stability, they are actually much MUCH better for bad terrain conditions (if you don't buy the cheapest model and think about its fit for you, that is). If you do mean your "all-terrain" requirement, look for the bulkier/heavier = more stable three-wheelers. A good example to check would be the German TFK brand even offering a convertible pramette type of bassinet to use in the reversed seat unit configuration. Even with any other brand, stop thinking about "lightweight and compact" when pondering which will be all-terrain enough (it doesn't go together).
My personal opinion is that three-wheelers are underrated, and those who'd truly appreciate the agile turning and bump-tackling will be delighted with a quality-made three-wheeled stroller. Of course, such a model requires at least some investment (it's not a cheap thing - but it has to last, you know, and good materials and know-how cost money).
Also, a 3W stroller is a MUST if you go running with your baby - nothing else will be stable and capable enough from a long-time point of view. For hardcore jogging or in-line skating on a regular basis, think even of a fixed-wheel three-wheeled stroller for sure. The use will be incomparable to anything else (and so will be the longevity). Not even talking about the comfort - think of the baby's safety, and always run ONLY with a stroller meant for jogging (as stated in its manual) and never with a carrycot or a non-harnessed-in child.