Weyard... what is the difference between Isaac and Matthew in terms of powers/abilities? Absolutely nothing. They can do the exact same things. What are the differences between father and son? Their names and their clothes. That's it. Nothing more, nothing less.
Hell, you wouldn't be able to tell the difference if Matthew got in SSB4 wearing Isaac's clothes as his default costume and bash the game after you read his name "Matthew". You would go into a nerd rage if Isaac got in SSB4 wearing Matthew's clothes as his default costume and then sheepishly take back your harsh words after you read his name "Isaac". Are you going to praise SSB4 for bringing back Ness and then erupt into nerd rage when you read his name "Ninten"? That's just plain silly.
Do not get me wrong. I am a fan of Isaac, Matthew, and the whole Golden Sun series. I call them as I see them. They are the same. They are even interchangeable in terms of protagonist roles in the series. The first Golden Sun is Isaac's story, circa 2001. Isaac got replaced with Felix because The Lost Age is Felix's story, not Isaac's, circa 2003. Felix got replaced with Matthew because Dark Dawn is Matthew's story, not Felix's nor Isaac's, circa 2010 (aka today).