Hmmm....as written it doesn't make much sense.
Do you mean "Concentrated acid has more _ than DILUTE hydrochloric acid"?
If so, then you could say "hydrogen ions in solution per unit volume".
But " concentrated acid has more _____ than hydrochloric acid " means nothing. What sort of hydrochloric acid? Concentrated? Dilute? And what sort of concentrated acid?
Also be careful with terminology: "Less concentration of water" doesn't mean anything - concentration refers to the number of moles of substance that are dissolved in water; you refer to concentration in relation to the solute, not the solvent.
Also, be careful not to confuse the term "strong" or "strength" with "concentration" when talking about acids. A "strong acid" means one that more readily dissociates in water - a "concentrated acid" is one that has a greater concentration (of substance) per unit volume of solution.