Out of the Options presented, im going with Deathclaws. Mainly because they are one of the most universal Threats no matter the character.
As a Melee Character:
Cazadors are pushovers, especially once you have the ballistic fist or similar, as well as piercing strike and super slam. They dont have high DT, or massive Health, a swarm is usually about 5-6 at once, throw a tin grenade at them at the beginning and then rush them and punch like a madman till everything is dead.
Ghoul Reavers are difficult, mainly because of high DT and high amounts of Health, but they are usually in small numbers, there's one, maybe two at once, and easy to deal with, just keep at it. In large swarms, especially with a glowing one around? Yeah best bet is to take the glowing one out first, otherwise thats gonna be a pain.
As for Deathclaws, well they suck. If you get one alone? Its a pushover, piercing strike, super slam and at worst a couple stimpacks, usually you can either KO them or knock them back avoiding their counterattack essentially, then just run after them so they cant jump you. However in a larger group, say 3-4 at once? Thats when it gets difficult, even worse when its more than that. Never take one more than 3 at a time. Rush the first one and kill it quickly, lob a grenade at it first maybe, then enter VATS and punch out the second, it gives you some room to breathe due to the slowdown, then deal with the third the same way as the first. If its more than that? Run like hell. And im going from the perspective of a high level Character by the way.
Ranged Character:
Depends essentially on the gun at that point, im going with a Sniper Rifle with Suppressor, its the safest method.
Cazadors, cripple a wing from afar, use vats. You will most likely get a stealth crit if you are crouched and either take it out entirely or at least cripple the wing, do the same to the rest of the swarm, alternatively, throw a tin grenade at them, or any grenade first, then pick off their wings and circle-strafe them. Without wings they arent any Threat.
Ghoul Reavers, aim for the head. Yes it sounds silly bit honestly its the best method, if you manage a stealth crit you can either take them out entirely if you are lucky, or cripple them outright, which makes them stand still, allowing you to fire a round in the leg or torso, crippling that as well, essentially stun them and then kill mobility. However seeing as they are usually not in large groups, its easy to deal with them from afar, picking them off one by one before they even notice you are there, or rather where you are.
Deathclaws, cripple the legs, whatever you do, cripple the legs. It makes them slow as hell, especially if you manage both. However avoid being swarmed, you can easily get hit by one from behind so stay as far away from packs as possible, take out small ones first, shot to the head usually does the trick and then whittle them down by keeping to move. They are only a threat if they get within range or its more than 2, you cant shoot fast enough if they get too close so that will be almost assured death on your part. At best, kill one or two from afar, then switch to a shotgun with DT Ammo, since they will either have spotted you by then, or are too close to deal with with a sniper rifle. If they havent spotted you, just kill the rest from a distance.