Work smarter not harder! Save your back use a wheelbarrow for those heavy (and not so heavy) lawn & garden chores. Save your wheelbarrow -- buy poly. Not only are they rustproof meaning the hopper should last for years, it is also a lot lighter than a traditional steel wheelbarrow. I don't think you are giving a bit of durability by going poly over steel.
This wheelbarrow also has a 16" tire to get maneuver over rough terrain relatively easily. Plus the tire is puncture resistant.
I opted for the 6cu ft model with wooden handles instead of the steel handle option. Steel handles get very hot in the sun; they also cost about $20 more than the wood handle set.
The fact that this is rustproof, lighter overall weight and has a flat resistant tire, makes this the one for me.