Best Gearing for Hills & Knees
 

Which of these would be better?

34,50
11 to 26

OR

36,46
12 to 25

Is one significantly better than the other for knees & hills?

The first has more hill climbing power and greater range. The second only really makes sense on cross racers, where it has the advantage that a front shift doesn't need to be accompanied the opposite way at the back - because the jump betwenen chainrings is so small.

34 f 26 r is hardly what most would consider a granny. My granny is 30 f 32 r and that is pretty low for bikes not set up for touring or MTB. To keep things reasonably easy on your knees, keeping a cadence of around 80 RPM or so without killing yourself is pretty good. It takes gear range to do that with the hills. Mashing the pedals kills your knees.

Any hard pedaling is hard on one's knees.
So to be able to conquer steep hills and still save your knees, get your gears as low as possible.
Why do you need a double chainring?
Why isn't a triple chainring an option?
I've got a 30-42-52 chainring with a 11-28 cassette ... this combination gives my higher AND lower gears than any of the combinations you mentioned.
The difference in weight between a double and a triple chainset is marginal unless you are doing races and I assume you are not doing any races since you care about your knees ;)
Why not simply get typical touring bike gears? 28-38-48 with 11-32 will give your a lowest gear of 28/32, which should be low enough for anyone to save his knees while climbing ... and the highest gear of 48/11 should definately be enough for anyone not trying to get his average speed over 20 mph.

I agree that the first one is because it gives you both a lower low gear for easy climbing and a higher high gear for running downhill.

I also agree that if you have knee problems the touring bike gearing would be even better. They generally go fairly high for high speed running and even lower than the ones you mention for climbing hills while heavily loaded. If you look around you can find close to the same gearing in trail oriented hybrids, if you want a hybrid. For example the Fuji Sunfire 1.0 is geared 26/36/48 and 11-32.

Ken

I have a bad left knee also, and if my saddle height is not right, to low, kills my knee....Richard

Who knows? I told him to get one - preferably from an MTB groupset - when he asked about Cross bikes.