It's a tricky one. In many ways, it comes down to personal preference and your given bathroom. First and foremost, if yours is anything like mine — small, that is — then opting for something slender and tall like the mirrored designs above is always handy. As the old architectural theory goes, if space on the ground is short, build up! Of course, you might be tempted to opt for the corner-style cabinets as these utilize dead space between walls — another space-saving cheat code to add to your toolkit. Equally, if you already have a sink, then the decision has been made for you: it needs to wrap around or slot under your pedestal basin.
Beyond this, you'll also want to consider finish. Bathrooms are moist places, so opting for a water-resistant surface is always wise. Plus, quality materials and sturdy shelving are a must — no one wants to reassemble a buckled cabinet. Check the capacity, and be sure it matches your load. Speaking for myself, I have a major moisturizer collection and believe me, it adds up in mass.