unless the sl-r is huge for you weight i'd stick with the mullet. Also depends on the terrain, if it is only going to be steep sustained pitches then its easier to get by on a shorter board because you can keep you speed up. If their is much mellow pow, or tree runs, the mullet will excel in these areas do to the increased float.
I'd almost certainly go Mullet unless your SL-R is huge or your Mullet is sized down. I also have an SL-R and it's fun and certainly better than a comparably sized cambered board in deeper pow, but anything deeper than maybe a foot and I'm usually wishing I had a dedicated pow board. In chest-deep, no contest, I'd want the Mullet (especially if it's pintailed... if it has reverse camber, that just seals the deal).
I rarely have issues with my SL-R in deeper powder even though it is only a 151 and im like 145...thats not to say my back leg doesnt hurt like hell by the end of the day in the super deep but its doable
'09 151 Never Summer SL-R
'10 K2 T1 DB Bots
'09 Burton Cartel Bindings
I have a Mullet for those endless pow days. Not complaining. It is so rad.
Diff'rent strokes, I guess. Its hard to beat a Mullet in the pow. If you like the SL-R more, then you do. I dunno, it seems pretty straight forward, you own both, and you like 1 more. *shrug* Why make thread?
Cats in the alley, Rats in my snakeskin boots
I just can't seem to shake the shackles of the City boy Blues