What's the difference between a game with a hundred levels, where you gain a level after every session, and a point-buy game where you gain another point after every session that you happen to play for a hundred sessions? Is it just the presentation?
Not quite. In a typical experience point to levels game, each level is wider than the one before, but value for defeating monsters is scaled by the monster, not the PC. So 20 orcs might level a level 1 party, but level 2 parties need 40. And level 3 need 120, or 40 baddass orcs.
In typical point buy only games, the points are awarded for playing, not for defeating enemies. Typically, 1-5, with 1 usually being "showed up"... and 5 being a real Wow moment.
I've seen several approaches with level based:
Levels reflect experience spent already, and are indirectly purchased:
- L5R, FFG's 40K RPGs,
- Tunnels & Trolls ed 7 and later
Level use high XP numbers to generate smaller numbers of advancement in character points:
- Rolemaster.10,000 XP gives 5-50 points to spend upon skills, but you can't spend on skills you haven't used nor trained... at least, RAW. Often played more lax.)
Levels regulate when XP are spent on stuff:
Levels result in increases directly:
- Tunnels and Trolls 5.5 and earlier. (When you level, you get level added to a stat, halved or doubled by utility of the stat.)
- Palladium (When you level, all skills go up; at certain levels, add new skills)
Initial is point buy, advancement is level based:
- Savage Worlds (I've got revised, which is fairly old) has 1-3 points a session, and every 5 is take one advancement; attributes limited to once per 4 advancements. The advancement is worth about 2 skill points.
- D&D 5E is also, to some degree. AL play is point build attributes, then apply class, race, and background; race and background are roughly balanced so effectively packages.
The Experience point systems used tend to correlate... but I see several broad categories
Low XP awards for categories of stuff, usually single digit, with high single to low double digit to level up: Savage Worlds, Alternity
Lots of low awards (double digit to low triple digit), high points required to level: Palladium (foes worth at most 25; a good idea is worth more); Tunnels and Trolls (Foes worth their combat attribute total or MR. Spells worth their casting total. SR's worth their total roll. attacks worth the damage taken or done)
Lots of moderate rewards (triple), high XP to level: Rolemaster (levels cost between 10000 and 500,000 XP each; pretty much every skill use is worth the roll * a difficulty mod; every hit point taken or delivered is an experience point as well, kill bonuses of 10 to 500 points whether killing or killed, loot, travel...) {I've seen a RM session where people leveled twice...}
Awards by foe's abilities, advancement moderate to high (scaling by level): D&D, Atlantean System (aka The Arcanum)
Non-leveled systems
Tend to use category based XP.
EG: Star Wars by FFG: points by length of session, plus additional for hitting one's motivations, and possibly for accomplishing goals (GM's discretion). Point costs same as in CGen, but not all items from CGen available after with Exp. Some items require indirect spends to obtain.
EG: Modiphius' Conan: points by session and GM appraisal 100 to 300, spend on stuff needing several hundred to several thousand to raise. Quite literally, as written, there's no reason to not have simply lopped off 1-2 zeroes from the end, other than the psychology of "2 xp sounds lame, 200 sounds plenty"...
EG: WWG 1 for show up, 1 for played traits, 1 for played them well, 1 for accomplishing goals, and 1 for prosocial behaviors. Costs to raise in the low double digits...
Some, like TFT, have a variety of categories worth multiple points, with a raise of a single point costing an amount based upon total attributes... this was not uncommon among small press games in the 80's.
It's more than just presentation, because it can tie into how XP are spent, and can (asin alternity) prevent acquiring bigger bonuses until later levels. Or, as with Savage Worlds, prevent certain categories from raising too quickly.