Houndoom is the better one for your team imo. It lets you deal SE damage to Psychic types threatening you potential Roserade/Toxicroak and it synergies well. If you get Flash Fire Houndoom and Dry Skin Toxicroak, both can deal with each other's weaknesses.
...Okay going with Houndoom. I used one in my last run of Platinum, but as you know Sinnoh's very lacking in Fire types if you don't have a DS/DSlite. But yeah, that synergy sounds like soemthing I can't pass up.
