I've been working with the cheap 21's for a few years now, until this year when i finally decided to drop the money on the 21 inch honda 216 Commercial mower. So far, im loving it. As others have commented, its a bit heavy, but it rolls great and the drive system does all the work of pushing the mower. Ive mulched taller grass, and it does fine. The bag system works great too.
can't speak on the walk behind, but there are some videos of the new toro commercial model 30 inch mower ( i think) called the turfmaster. if you do a search on here, you will find a few videos of it. It might be a good option if you dont need the full blown walk behind.
Good luck with your decisions.
My Primary Equipment:
2000 Chevy 3/4 Ton Long Bed 4x4
6.5x12 Dual Ramp Trailer w/ trimmer and blower rack
2012 21" Honda HRC-216 mower
2013 Exmark Commercial 30
20?? Gravely ZT1534 34" ZTR
Mclane 25" Reel Mower
2010 Husqvarna 21" mower with Honda engine
2008 Stihl FS250R Trimmer
2010 Stihl FS90R Trimmer
200? Stihl FC75 Edger
2013 Stihl BR 600 Blower
2013 Stihl SG20 Back Pack Sprayer
2013 Stihl HS81 t Hedge Trimmer
200? Billy Goat AE550 Core Aerator