Here is my opinion, yes, for more details read on.
So these numbers reflect my skills in mining so numbers will always differ;
Mining V
Mining upgrades IV
Plagioclase processing IV
Expedition frigates II
Astrology V
Science VI
Deep core mining II
Mining drone T-2
Endurance T-2 mining frigate No boost, No mining implants, mining Plagioclase
621 units per 1 cycle mining drones T-2 (214m3)
6070 per cycle @ 180 sec (3 mins) Deep mining core miner T-2 with T-2 mining crystal (2124m3) X 3 mining laser upgrades T-2.
Prospect
2 X Deep core mining lasers T-2, T-2 Plagioclase mining crystals, 4 Mining laser upgrades T-2
3639 units per laser = 7278 units of Plagioclase per 180 sec cycle (3 mins) 2547m3
Venture
2 X Deep core mining lasers T-2, T-2 Plagioclase mining crystals, 1 T-2 Mining laser upgrade, 2 T-2 Mining drones.
171 units per cycle X 2 = 342 units (T-2 drones) no rigs, 119m3
2554 units per T-2 deep core mining laser with T-2 Mining crystals 5108 units total = 1787m3
So there are the numbers I got, worth it, hell yes, even without drones the Prospect shines above them all.
So using them I think has been largely ignored because people always want a barge or exhumer but never consider how effective Mining frigates are when properly fitted with the top of the line mining lasers, if there is a booster and hauling support the ability to quickly traverse asteroid fields will be really appreciated as barges slow boat around, the one thing barges like the procurer have is protection, the main protection Expedition frigates have is the ability to scatter or cloak, fitted with an afterburner or microwarp drive, most gankers will be fitted with blasters and point quickly with sensor boosts, running from their range is best, bit of strategy and no AFK and you’ll be good to gtfo if trouble arrives.