Block heels are the only heel I trust for a full day on your feet, because the weight goes straight down through a wide base instead of wobbling about on a point the size of a two pence coin. If you've ever stood at a bus stop praying the ground stays flat, you'll know why that matters.
Keep them away from anything already heavy at the ankle, a cropped wide leg trouser or a thick sock peeking out, because block heels have enough visual weight of their own and the two together just look like you're wearing furniture. They sit best under a straight or slightly flared trouser that skims the top of the shoe, or under a dress or skirt where the leg does the work and the shoe gets to be the quiet, sturdy bit underneath. When you're trying a pair on, check the actual height of the block rather than trusting the word "mid" on the label, because a mid height block at the front of a shop and a mid height block in a different brand can be a full inch apart, and that inch is the difference between fine for a nine hour day and fine for getting from the car to the restaurant. Look at how the heel meets the sole too. A chunky rubber cap that wraps slightly up the sides will outlast a heel where the covering is just glued flat and starts peeling at the edge within a few wears, usually right where it catches the pavement.
Leather and leather look alikes behave very differently once they've done some miles. Real leather will crease softly across the toe and mould a bit to your foot, which is no bad thing, but it needs a proper polish and occasional conditioning or it dries out and the creases turn into cracks. A faux leather or patent finish keeps its shape better in the short run and wipes clean in seconds, which is handy if you're walking anywhere near a puddle, but it doesn't forgive scuffs the way real leather does, it just shows them. Either way, rotate two pairs if you can, because a heel that never gets a day off compresses at the ball of the foot faster and starts tipping you slightly forward, which is where the real ankle ache comes from.
They're the wrong choice for anything genuinely dressy where you want height without bulk, a block will never read as delicate, and they're not much use on soft ground either, a thin heel sinks less than you'd think but a wide block can actually catch and drag on grass or gravel.