I don't like that this turns into an either/or decision or debate.While "monsters use the same format as PCs" is fine from the player side, It gets unwieldly from the DM side FAST as levels increase. And the problem is monster's are not PCs - they are designed for a completely different purpose (for the DM to use as opposition) and anything that helps the DM toward that purpose is a big plus IMO.
Let pcs and monsters use the same FRAMEWORK (to an extent), but the monster BLOCK can be more COMPACT, representing only what you need quickly for combat or rp.
I.e. mostly like it currently is/was in 5e.
Avoid the extremes of monsters built completely different or having full character sheets, but use similar rules/framework.*
*I mean. all the way back to 1E, I most certainly did not flesh out the 18th bad guy necromancer as a full pc, merely used/planned his main actions and maybe gave him a special ability.