so there are actually 3 options here:
1) pentax 17-77mm f4 SDM : ~$480
2) sigma 17-77mm f2.8-4.5 DC : ~$370
3) sigma 17-77mm f2.8-4 HSM OS : ~$450
the problems i see for pentax are: SDM only (boooo! - make sure to have warranty!), no WR
and a small price premium over sigma. however, pentax gets bonus points from me for quick-shift focus and a smaller filter size but some people might not care about that.
for the newer sigma, i think OS is overkill and waste of money on pentax bodies and HSM can suffer from the same problems as SDM.
the older sigma is f4.5 as opposed to f4 but has the gool-ol' screwdrive and is a bit cheaper.
both are also variable aperture, which probably won't bother some people but i've been spoiled by my primes so i prefer constant aperture.
so unfortunately they are all compromises. if only pentax made a WR SDM-or-screwdrive (and a firmware upgrade to let us select which to use) version of the 17-70mm... sigh...
Last edited by pb_red; 04-21-2010 at 05:14 PM.
Reason: counting to 3 is hard...