Ok, Ok... Im guilty of the football quote
Go with the 1300, my guess is the BTU rating is low on this unit! (even that small one looks like a big square beast to me).
I will say it does appear to be constructed good and I like their natural occurring heat exchanger tubes (pretty damb smart).
the airwash holes look like the grand canyon (but hopefully they will fill up and clog in time because being that large damb sure wont help function).
I cant speak for that grate at all, I guess it does not warp out (though it sure looks like it would), and I guess it functions ok because nobody complains about it (it better because you don't have any second options for slicing by the look of it).
Easy replace firebrick is certainly easy & cheap to replace whenever needed, It does not even look like its cemented in
(some pluses & minus to that).
get the 1300, if that Sponge Bob Beast cant heat your house somethings wrong!
Don't forget to post up some pics when she's up