What are the pros and cons between regular flashlights that use standard alkaline AAA, AA, C, D, etc vs. those lithium batteries such as 123A in Surefire lights? Do these special batteries last longer unused? Create stronger light but does it die out faster? What about corosion like how alkaline batteries leak? How easy is it to get in emergencies?

lithium batts have a higher discharge rate, longer storage times, dense energy storage but are more expensive than alkalines
alkalines have a lower discharge rate, lower voltage and are more prone to leakage. cheaper.

most of these CREE LEDs need a high discharge, high voltage battery to produce high output light.

So for tactical use going with lithium flashlights would be better. But for emergency use such as storing in a BOB would it be better to have longer storage or longer use when needed?

So for tactical use going with lithium flashlights would be better. But for emergency use such as storing in a BOB would it be better to have longer storage or longer use when needed?

Batteries wear out even when not in use.  Eventually, they all have to be replaced. 

For a good example of what we ought to do, look at the emergency lights in government buildings.  Someone has to go around once a month and test them for proper operation in a power outage.  Occasionally, the batteries need to be replaced, even if they were never actually used in an outage.  The fixtures also might need replacing.  Unless you test, you won't know until you need them.

Get in the habit of swapping batteries periodically in your emergency flashlights.  I have some spare rechargeable batteries that fit all my weapon lights, daily carry lights, vehicle emergency lights, and household emergency lights.  It's nice that they all use one or more of the 123A rechargeables.  I rotate the batteries about every two months.  I  replace the batteries in a couple of flashlights with spares that are fully charged, charge the ones i remove, and repeat replacing and recharging until they all have freshly charged batteries.  I'll keep the spares charged in case we do actually run a set down from use.

During the battery exchanges, you are testing the bulbs, switches, and batteries for good operation.  If you find a bad one, replace it.

There's no "best solution" for batteries.  Even the best batteries won't last indefinitely.  Rechargeable are a good hedge against a real emergency.  All the stores might be out of disposables, but you can recharge with car adapters, generators, commercial power if working, solar chargers, etc.

Just my two and a half cents!