For volume(sound) maybe but the 2 penguins will filter more water and are a bit easier to clean. I love my xp's but I still use hob's for my 60 gallon.
Depeding on how old your XP3s are, they will eventually leak and you will have to repair them if you can. I have two XP3s that leaked. I use Aquaclear HOBs and they never caused any problems.
Fluval has a new line of HOBs that claim loads of bio. I love my emperor 400 though. I had one on my 55 with a 20in clown knife and lots a phew other friends and it did great. I often thought of adding a second but never really needed it. Bio-wheels are great!!
Depends on what your stock is. I prefer Canisters over HOBs, but HOBs are a lot easier to clean. A Canister holds more media and doesn't need as much maintenance.