A lot of people say that Liches are stronger than vampires, and the truth is: Yes; the average Lich needs to be at least capable of casting high level spells(7/8/9) while the average vampire just need to be LV 5. Both offers diferents benefits and downsides so i will "standardize" an setting.
- The character wants to become an ruler
- The character is a lv 18 caster
- The character wanna more time because he is already an 55 year old human and must decide between lichdom or vampirism to have more time to realize his dream
- The character is relative wealth but not to the point of recruiting an big mercenary army or bribe high nobles
- The 3 neighbor kingdoms have an population of around 0,8-1.2 million each, and an mutual defense agreement
- Each kingdom have some(3-5) lv 18-20 heroes nobles, most of then melee warriors but some cleric/casters and all of then have access to epic(+%) weapons.
- Most soldiers are around lv 3-7(recruits/veterans) and most nobles was submeted to a harsh training since his childhood so his overall level is 10-15(with few exceptions) and most members of high mobility have access to +2/+3 weapons, around 10% of the country population is of soldiers. Veterans have access to +1 weapon in general
- The character knows that in his lifetime, there are no way to build an force that can surpass the enemy. He must use strategy, diplomacy, etc; after becoming immortal and as a high level sorc, he can find ways to have an lichdoom potion or to capture an vampire and turn himself into a vampire and kill his "sire" in the process.
What "cheat death template" is the best one to him, he needs to build an considerable force, become much stronger, accumulate wealth, find a lot of powerful servants, etc and have a lot of time for it(since he will be immortal).
My honest opinion, for "Rule by force", Lich is best, for rule with Charisma, vampire is the best, for a Wizard, Lichdom fits more and for a Sorcerer, Vampirism fits better. Any troughs? IMHO the life as a Lich is not a good life, if living isolated, without being able to taste food, to have pleasure, being just a living decayed corpse...