I say, is it too much to ask for both?
Use them in tandem is really the way forward, I think, complimenting each other and getting the best from both. See that enemy unit with the AP3 that will tear up the Death Co? Send them a SangGuard squad that doesn't care, leaving your
DC to take out those 2+ save units with volume of attacks that the
SG can't match. Death Company are a blunt force instrument, and their strength comes from just bludgoening the enemy enough that their saves and wound count don't matter. SangGuard, on the other hand, are a scalpel, used for targeting specific threats that the
DC would either overkill (if it's too small a squad) or take serious damage against (high
Init targets, AP3-heavy units).
Both are excellent units, and work together well. This, as mentioned above, also throws up a lot of target priority issues for the opponent.