Kris's photo looks like a mgnifica to me, but clearly not enough info here for a positive id. The thing that does it for me is the solid tips to the tentacles that are comon in magnificas and rarer, but no unheard of in BTAs.
I lean slightly towards magnifica also with the original poster possibly because of bias since I have a small magnifica with almost identical base color that shows no verrucae (sp?).
In my experience, how it plants its foot once it settles and starts growing always tells the id ( unless it climbs the glass, then you still may not know) Going under a rock after shipping is not uncommon for a magnifica.
I'll throw my experience in too seeing many BTAs with bifurcated tentacles and magnificas with bubbles. The bubbles on magnificas I have seen look like the little distinct balls a bit down on the tentacle and the magnifica will have a pointed tip slender tentacle at this time. At other times (coinciding with lower flow) that same magnifica will show the blunt ended or bubbled ended tips and thick tentacle that the above photo shows.