But then you lose access to 3rd level spells.
Keep it Sorcerer 6/Rogue 1, definitely.
Gotta ask what 1- 3rd level spells do you just have to have?
and I f you have to have third level spells then a sorc 7 is preferable.
1 spell, +1 WP save
Evasion --- and double the skill points...and on average HP.
It's not as cut and dry as you might think.. Especially given the fact that you can get stuck without a rogue.
I guess that depends on what 3rd level spell they hand us...but as a sorcerer, you get to cast that spell several times (and 1 more time if your CHA is high enough).
ynnen pointed out that XCrawl is different than a standard tournament, so you may have some insight that I don't here (so keep that in mind). I see spellcasters as easy ways out of time-wasting combat. I would much rather have access to a 3rd level spell that can do more damage than throw a warrior at an encounter. I guess this is also just my personal preference.
If they're looking to provide an alternative to the higher level rogue character (in other words, for groups not looking to take that character), then it would make sense to do as you say - 5th sorcerer and 2nd rogue.
I would probably take the higher level rogue though, so I'd prefer the sorcerer level be pushed up to give us access to a third level spell.