Gad Guard

Gad Guard is basically a deconstruction of the light hearted "boy with partner robot" genre that Medabots embraces.  

Both series deals with the idea of robots with the main protagonist exploring the idea of robotics with the help of people he meets. Hence, Robotics;Notes and Gad Guard adapts science fiction themes. Both series has drama, comedy, and some emotions. Gad Guard has a more serious approach while Robotics;Notes has a more lighthearted one. However, both series gives off a similar feeling. Both series also features the exploration on the origin of the robots and how they function/are used.  

The theme of science fiction are apparent in both series. But additionally, there is light comedy, drama, and later slight romance as the episodes progresses. And of course, the bonding with machines and building a relationship with them are also present in both anime(s).  

its a matter of storytelling and execution. B'tx is a better youngsters and mecha show than the mediocre modern gadguard serie. Both deals with young teens wich life are changing with their mecha discovery, and then the overly stereotypical gadguard chara with ' I don't want to go with you' wich turns a complete 540 degrees in a microsecond, Bt'x has less that kind of problems  

In both animes, mechas are used to fight evil and bring forth the proverbial peace to the world. In Regalia, humans fuse themselves with the mecha while in Gad Guard, the Gad activates and manifests itself to a Techode or Gadrian once it reacts to a person's positive or negative feelings, respectively. 

There both set in a future after a great disaster happen, mechs or spaceships, both stories surronding misfits that find a purpose in alliegal or shady bussiness and great music. 

The side effects of the mechs used in either series has similar consequences 

In both the Main characters has relationship with the living mecha. 

While GetBackers and Gad Guard both go in completely different directions with their stories, they both have the same urban feel and similar character interactions. On top of that, they have similar upbeat music and intense action sequences. GetBackers contains a good bit more comedy than Gad Guard, but Gad Guard still has a fair dosage as well. In conclusion, if you like the overall atmosphere of one of these series, you would probably find a sense of familiarity in the other and like it, at least to some degree. 

Westernized, stylish teen superhero show where the kid has a giant silent robot companion. 

Similar animation and steampunk action/drama 

Both have a young main character who own and fight with a mecha.