All the three in one gives you is a side discharge if you do not want to bag or mulch. It will not improve performance.
Make sure the engine is running at the proper speed with a tach. I have been finding engines running 200-300 rpm too slow out of the box. A local shop might check and adjust it for you for a nominal fee.
Is your grass thick or wet? How much are you taking off? All the mowers you are looking at should so a decent job under favorable conditions.

How tall is the grass you are trying to mow? If you're trying to mulch more than an inch of damp grass, you're probably going to have trouble.
Mow a narrower swath-

My 2-in-1 is mulch or side discharge. No bag. :( I probably wouldn't need a new mower if I could bag.

The mower I have is a few years old. It may be running too slow, or some part could be going bad. I don't know enough about engines to do anything without taking it in. The grass is thick because I've been good about fertilizing, seeding, aerating, etc. I have the mower set to maximum height of 3.5" and tend to mow every 6 days, sometimes 5. The grass grows fast though, and can be 2" to cut off. I wait for it to get dry, but it still struggles even after 5 days of no rain and hot sun. Thanks for the help.

Kmfisher:

Since you seem to be cutting high enough that the grass can side discharge or spray out from under the mower, here are some suggestions that will work for your current mower or even a new one.

Most cheap mowers have cheap shallow decks that can allow quick grass buildup underneath which will effect air flow.

Buy bigger wheels. A lot of the cheaper fixed axle mowers come with 6" wheels. If you get 7" or 7.5" wheels, that will give you slightly higher clearance with more room for the grass to blow out from the discharge chute or out from under the mower.

Get yourself some generic high lift blades. The high lift blades cause more air flow which should help by giving you more force to throw the grass out.

Buy a Snapper PUSH model 21" mower that uses the same deck as their self-propelled units. The shape of their deck creates fantastic air flow and I think all of their blades are high lift.

Good luck!

Fairyprincess

The first comment about the rpm speed might be the clue. On the inexpensive mowers it's so easy to bump into a pine tree branch and bend the thin metal tab which controls engine speed. I've seen many knocked down 500 rpm or more just by hitting a branch.

Is there a place where I can adjust this tab? It's a Tecumseh LEV 90-120 engine. I'm not concerned about blowing it up since I am already planning on getting a new mower. Thanks.

I'm not familiar with all the models, but if I saw a picture, I could tell you. It's not something you can do by ear though.

Here's a picture I found on a small engine forum. Mine looks just like it. What do I bend and which direction? Thanks.

{{gwi:130028}}

I have an issue...I want a good little push mower that the wife and I can trim the yard with. Our local dealers (only have two) carry Troybuilt (says he has to to compete with our only two stores Wally world and Lowes, and the other carries Husqvarna. The Husky dealer has the 7021p for $260.00 and says it is a real good mower.

Everyone seems "commercial crazy" and that is way overkill for my needs and my budget. So...is the Husqvarna 7021p a good mower or not? I can get Honda, John Deere, and Troybuilt at Lowes, also Brute and Yardman at Wally world. Not a great selection, other dealers are at least an hour away.

Thanks,