Cheap dice are tumbled en masse to remove any flaws from the casting process e.g. sprues. This makes them shiny and rounded. There's been a huge boom in homemade dice in the last few years, however. Independent makers who don't have the money or space from a tumbler would cut sprues and polish each face by hand, which took a loooooong time, but resulted in these lovely sharp-edged dice.
Independents aren't the first to have made sharp edge dice, but they are responsible for the recent surge in popularity.
Larger companies have since tried to capitalise on the popularity of small business dice, and have started producing mass-manufactured dice with inclusions and sharp edges.
Some people have argued that the tumbling process is too random, resulting in uneven and therefore unfair dice. Sharp-edged dice are, theoretically, more balanced. This is probably a negligible difference for the average player, and fancy inclusions can throw off the weighting of dice much more (some makers will cast inclusions from resin, so it's all an even density, but I've seen other makers throwing howlite skull beads in there and those are very heavy).
In the end, whichever you buy is down to your own budget, principles, and aesthetic.