well I have owned both and the rl-p wins in sq hands down no contest. As for spl I would say they were pretty close to my ear although I never had them metered so I couldn't tell you for sure. For a daily driver I would def choose the rl-p over the hx2 anyday.
well i have 6 power hx2 15's in my navi..in a bandpass...and they get loud to the point where u can stand 5blocks away and u would think my truck is next to u.....so spl its great....sq..sad to say sounds like shit...thats why i got an epicenter...to help it out alittle bit