Last time that I checked around, Sequence only has external pumps, no submersible.
When I bought my Pondmaster, Gene told me that he suggested them for submersible pumps.
Evidentally I have been very lucky with Laguna pumps because for a cheap pump they've been very good for me, I have been running them for 6 years now along with my two Pondmaster and Sequence and have had to replace one of them.
Guess like everything, there is good and bad experiences.. I won't use any pump if they use alot of electricity so I don't know about other brands except for them.