I'm looking to buy a new walk behind edger that has a stronger construction, but doesn't break the bank.

Suggestions?

To answer your question more accurately, I think a McLane 101 with Briggs for $325-$350 would be your best bet. The 801 with Brigss is more ($400) but has additional features. I would avoid the 137 with Briggs. It is only about $20 less than the 101, and is "dumbed-down" with fewer features.

For homeowner use, a convertible string trimmer with a blade edger head often makes sense. However, you'll never get the "knife edge cut" with a nylon trimmer. Of course some folks don't care or can't tell the difference.

As for "never seeing pros using walk behind", the writer must not get out of the house very often. Wheeled edgers are still commonly used by professional gardeners in the South and on the West Coast, where crawling grasses like St. Augustine and Bermuda are prevalent. Same gardeners also continue to use front throw reel mowers for quality of cut. Of course, those customers who don't care, or can't see the difference, will let their gardener use a rotary mower and string trimmer to save a few bucks.

As in the rest of life, you get what you pay for.

Storage wise it is takes less space to store the stick edger, and that is one reason that the stick edgers appeal to the lawn services. The stick edger will ride on a rack and not take up valuable trailer space like a walk behind.

I have looked at the McLanes before, and would agree with the previous poster that they might be your best bang for the buck. If you could find a used Deere E35 however, I would recommend it. They have a Kawasaki 3.1 hp engine and a convenient curb hopping wheel, and remote air filter. It is the nicest walk behind I have ever used. A photo of one is below...

I have also never seen a lawn service use a walk behind, but the level of service in Central TX im sure is not what it is elsewhere.