I've recently had 2 bikes (Trek and Giant) of the hybrid style. The frame style was comfortable but both were difficult to change gears. When going up an incline, I would shift to a lower gear. The chain would slip, pop, clatter, and sometimes fall off completely. I took them back to the dealer who adjusted the shift cable but that did not correct the problem. I got rid of both of them. Is there a bike that does not have this shifter problem? thanks
A bike chain falling of the cogs is a clear signal of a bad adjustment of the high and/or low limit screws. This has nothing to do with cable tension, so it can't be really solved by just playing around with this variable.
Anyway, this kind of adjustment is super easy, and even if the derailleur no longer works, that's no reason to throw the bike away: you just need a new derailleur!
I'm guessing that you're having this problem with the front rings.
Rear cogs these days often implement a system invented by Shimano called "Hyperglide". It's a set of ramp-like grooves carved into the cogs which allows the chain to derail easily and engage two cogs at the same time, greatly easing downshifting, even under load. (Video).
There is also a different "Hyperdrive" system for chainrings, which is less ubiquitous. It involves some "in between teeth" that engage the chain. (Video)
For minimum shifting fuss, get a bike which has hyperdrive in the front, hyperglide in the back.
Now, Hyperglide cogs are very common on bicycles, seen on even low-end bikes. On the other hand, Hyperdrive is less commonly seen.
If you're on a bike with only Hyperglide (very likely case), and you have to shift while climbing a hill, use the rear shifter first. Then, if necessary, downshift the front. If you down-shift the rear cogs as much as possible, you reduce the load on the chain, as well as spin the pedals faster, both of which facilitate the front shift.
There will always be some rattling when you shift the front rings under load. This is because the movement is done by a crude metal guide which simply pushes on the chain sideways. A chain that is taut due to the intense tension of climbing a hill is hard to displace. You cannot have a chunk of metal pushing on a tight, moving bicycle chain without a clattering sound that endures for at least several seconds.
As far as the chain coming off the front rings goes, that is a problem you cannot entirely eliminate in the mechanism. That is, not without some downside. If you set the range-limiting trim screws so strictly that the chain never comes off no matter what, it will be be more difficult to shift into some gear combinations.
The fix is to get either a friction-based shifter for the front rings, or an indexed twist shifter. These types of shifters let you easily play with in-between positioning during a shift as well as control the speed of the shift and the amount of force applied. This is necessary because the amount of displacement needed to move from one ring to another depends on the angle of the chain, which depends on which gear is engaged in the rear. At least for the front rings, stay away from the trigger shifter type which is semi-automatic and takes shifting control away from you.