useful or not? useful to whom?
this pair or ad weapons have passives where one spend mana for damage but another gains mana by aa
is it powerful? useful to high mana costing adc?
this pair or ad weapons have passives where one spend mana for damage but another gains mana by aa
is it powerful? useful to high mana costing adc?
Jayce and Urgot can use them both well. It's more of an AD caster item than an AD carry item, but marksmen who spam abilities can also make good use.
Are you talking about building both or situations where one is better over the other?
If the former, you'll get better DPS from a more conventional build like BT IE PD, and you should only ever need one mana sustain item anyways. Plus the Mana return is only for your autoattack and doesn't get returns from the muramana on-hit.
If the latter, then Muramana is better on characters with spam spells or generally poke-heavy champs(Jayce, Ezreal), while ER is basically for ADCs who would rather have 10%CDR than 10%lifesteal(Lucian, Sivir sometimes).
These two items sort of have their uses.
Muramana is great on a lot of DPS-based champs who need mana. It's considered a staple on Jayce and Yorick, and it works well on Ezreal. It also can be used properly by any Marksman, considering it's efficient on the AD alone, grants a ton of Mana, and that active actually deals okay damage. It's just not considered very efficient on most of them, because it doesn't give near the same damage output on most of them.
Essence Reaver is kind of...pathetic. Most people don't buy it for the mana vamp, they buy it for the massive stick of AD with a bit of CDR on the side. Sure, the mana vamp is a nice bonus, but by the time you have it, usually, most champs don't need the mana sustain that much anymore.