Arc the Lad

Plotwise it's not very similar, however you'll find the same atmosphere and pressure in both anime: the music is kind of alike and the internal conflict in the main character persists same way. In both of these the main character isn't the strongest (Elk is weaker than Arc). In both anime you'll find these kind of experiments on people and manipulation of people. Clive is as cold as Joker and there's the relationship Wendy- Joker and Clive - his assistant. Arc and Anita are kind of similar since they both have conflict with the past and they are full of energy for fight. Also in the end the situation is crucial in both anime, because the world is covered in darkness and manipulation.  read more 

Both anime were developed by Bee Train and are based on Sony PS1 games. Very similar in art and style as well story progression. If you enjoy one you will enjoy the other 

Both are based on popular JRPG series made by Square Enix and features edgy characters being put into dangerous situations with their partners. 

Both are old school fantasy anime. They have same atmosphere, even the worlds are slightly similar (magic+some techno stuff). Even Elk and York (main heroes) looks the same.  

if you played the game "arc the lad collection" on ps1 then youve watch the "arc the lad" anime then i recommend "star ocean ex" because its also a game in ps1 "star ocean till the end of time" 

Both anime have lot of humans that get abused/used to succeed with an evil plan in a certain organization with two faces. There are also many chimeras, experiments, humans with different powers and other similarities. If you like adventure and one of them, you may like the other one. 

Both are Bee Train productions and both involve some forms of sword and sorcery. 

Although the stories are very different in tone, both Arc the Lad and Scrapped Princess are "Swords and Sorcery" fantasy anime that also have some underlying sci-fi elements.