Depends on what you're looking for really. Pokemon Red and Blue have more easily accessible glitches whereas Pokemon Yellow requires a few more hurdles to even get some of theirs working (an example of which being Missingno. which is notoriously difficult to capture and use in Yellow due to Game Freak taking steps towards stopping it, but it is possible.)
Pokemon Yellow is known for throwing in anime references here and there, like Red wearing the same Pokemon League Expo hat and uniform as Ash Ketchum does, Team Rocket's Jessie and James with Meowth as a Pokemon showing up, and a few other things. It's also known for being the game that can net you all the starters legitimately (it's technically possible to get the other starters in R/B via glitches), for example Officer Jenny giving you a Squirtle after beating Lt. Surge.
The only real downside to Pokemon Yellow is that it is considered far and wide to be non-canon with the rest of the game franchise/timeline, with Red and Blue instead filling the role. The sprites while cleaner and more tuned to the anime are also less interesting to look at than the Pokemon Red/Blue sprites which sometimes have hilarious proportions. (This is just my personal opinion as a sprite artist since it's fun watching the Pokemon sprites evolves from RG to RBY to GSC.)
Pallate colors in Yellow will be Gameboy Color compatible while Pokemon Red/Blue is in monochrome. To be honest I was slightly disappointed with the lack of Super Gameboy pallate, but it hasn't bothered me all that much. Red and Blue are honestly still fun to play. Yellow also contains a Pikachu Surfing game, but really it's more of a sort of score minigame to see how much points you can rack up and as far as I'm aware doesn't do anything beneficial to the main game.
I'm not sure where you got the idea of Legendaries being in different locations but this is not the case in either game; they remain exactly where they were between the two, with most likely only changes being made to the dungeons or caves they were in.
In the end I guess it follows like this;
If you like more easily accessible glitches, funny looking sprites, a canonical plot and don't mind monochrome, then Red/Blue is for you. (If you choose this, pick Blue. You can get Porygon much cheaper at the Game Corner than in any other game.)
If you prefer more anime-looking sprites, an anime albeit non-canonical plot, all starters, color and don't mind having trouble with certain glitches, then Pokemon Yellow is for you.
