Level is not the only deciding factor in a fight.
Although Digimon of the same level can be considered to be on par with each other in a general sense, there are exceptions. For example, Lucemon is described as a Child (Rookie) Digimon with power greater than a Perfect (Ultimate) Digimon, while Lucemon: Falldown Mode is an Ultimate Digimon with power exceeding Mega Digimon.
Although neither Angemon nor MagnaAngemon state in their Digimon Reference Book bios that they're particularly strong for their level, the descriptions do imply that their natures are oriented towards fighting evil.
Furthermore, the primary three attributes or types into which Digimon are classified are Data, Virus, and Vaccine. In the virtual pets, this is used as a sort of rock-paper-scissors mechanic, with Vaccine having an advantage over Virus. As one might infer, Angemon is Vaccine-attribute while Phantomon and Piedmon are both Virus-attribute.
In conclusion, we can infer that Angemon/MagnaAngemon is intended to be more powerful than other Digimon of the same level, at least when fighting "evil"-natured Digimon.