Dennou Boukenki Webdiver

Similarities: - They are both sci-fi anime, set in a technologically advanced world. - The two anime deals with human and the virtual net world. Difference: - In Webdiver, the kids pilot the robots to bust the viruses while in Rockman, humans plugged in a program to bust the viruses in the virtual net world. 

Similarity : + Action-Adventure anime set in Virtual MMORPG Different : + In webdiver player using mecha unit to fight enemy + In accel world player avatar is equipment with armor-like mecha to fight other player  

Digimon Adventure 02 and Dennou Boukenki Webdiver are similar in terms of story: -Both are about a group of children who fight amongst a partner. -In a digital world, but it also affects the 'real' world. -No spoilers, but some characters have similar storylines/traits in both series. The difference is that in Webdiver the partners are robots, in Digimon they're monsters. If you liked the story of Digimon, you'll probably like Webdiver's story as well. 

Similarity : + Action-Adventure anime set in Virtual MMORPG + Players trap inside game and only can be escape after defeated the main boss (Heathcliff & Deletloss) Different : + Compared to SAO, webdiver is lack romance between character + Kento Yuki (Webdiver MC) not trapped inside game like Kirito(SAO MC) 

Similarity : + Action-Adventure anime set in Virtual MMORPG Different : + In webdiver player avatar is same with human version but in hack the player even can choose opposite gender + .hack// is almost like MMORPG (farming & leveling), something not found in webdiver 

Similarity : + Action-Adventure anime set in Virtual World Different : + Animatrix is more dark & mature compared to webdiver  

Similarity : + Transformable mecha units + Each mecha units can be merged into one single unit Different : + Webdiver set in Virtual MMO + Juusou Kikou Dancougar Nova set in real world 

In both anime, the world has gone computerized and virtual; and children spend their time in the virtual world. Additionally, the kids are being attacked by a thing that is supposed to protect them: in Dennou Coil, it's Sacchi; and in Dennou Boukenki, it's the Web Knights.