B boards were originally intended for small business use. The onboard headers tailored more towards storage use, lack of multiple fan headers, even the factory software was setup more for raid/fast cache storage with smaller SSDs etc.
H boards were originally intended for the average homeowner. Grandma's web surfer, HTPC, 10 year olds gaming habits etc. They came with most of the bells and whistles that you'd find on the Z boards, but performance wasn't really intended to be anything more intensive than plug and play.
Z boards were originally intended for Enthuziasts. Overclocked, boundry pushers, gotta-have-its but no idea what it does type ppl. Z boards have everything in the bios unlocked and available for tweaking, tinkering, bluescreening etc. As long as the cpu supports such.
Today, it's all about the Bells and Whistles. B has minimal, it's a serviceable mobo that usually has just enough to cover most ppl actual needs. H has almost everything, but tweaking is limited to lowering, not raising beyond stock. Z is king, if it's a Bell or Whistle, it has it. The more expensive the board, the more it has.
Nobody Needs more than a B. Most ppl prefer more. Some ppl insist on the more from a Z.
If you never intend on any OC or uber performance tweaks, a B or H is fine. If you have a locked cpu, B or H is fine. If there's Any consideration or deep thoughts or flipping coins about OC, get a Z. It's better to pay a little more up front, just in case, than have to replace the mobo later when bitten by the OC bug and a pocket full of regrets.