Sigma 17-70 OS or 18-55 IS II + 55-250 IS

A new thought.

I was looking at getting the Sigma 17-70 OS as an upgrade to replace my 18-55 NON-IS kit for my 30D. I was contemplating selling my 85 1.8 (which for obvious IQ/bokeh reasons I absolutely adore) to help fund the acquisition, but just recently thought of instead of getting the 18-55 IS + 55-250 IS instead. The IQ that any of these provides is certainly an upgrade from what I have, but the 18-55 IS looks to be a fair amount better than the Sigma, albeit a bit slower, and the 55-250 would give me a LOT more reach for chasing my daughter around the playground / outdoor shots though with a lens change involved.

If a bit more background is needed, you can take a peek at my original post here

So, POTN gurus, what are your thoughts? I can get the two EF-S lenses for ~$300 I'd say, and the Sigma for ~400 (promo for $420 new, now) or a bit less used perhaps.

Thanks in advance for the feedback.

Oh, also, is there a big difference between the EF-S 18-55 IS I & II? Has anyone used both?

mikefike wrote in post #14578226
but the 18-55 IS looks to be a fair amount better than the Sigma

It really isn't, I replaced my 18-55 IS with my sigma 17-70 OS. The siggy is better in every way.

Not that I know of, besides the "II".

If you can swing it, go for the 17-70 + 55-250 and you'll have a great setup. The 17-70 makes for a wonderful travel lens, and you have the 55-250 for when you know you need tele.

I just snagged a used 17-70 on saturday and I have been fairly impressed with it.
Very sharp up to about 50mm and about kit lens sharp from 50-70mm.
The fast wide end comes in handy too

I just got the 17-70 OS 2 weeks ago and so far I love it! Build is better than I expected. Nice and sharp good colors. For the price you can't beat it.