Well, I've always liked keeping them on for safety purposes and looks.
But I've also cussed every time I have had to unbolt and remove them and so forth.
A lot of crap builds up in there around the driveline and it sucks.
However this is another little positive detail that I really like about the Lesco Z-Two.
It has diamond plate covers that do not contact the decktop itself...
And it has these cool little rubber quick latches that hold them on.
They come off in a flash for cleaup and greasing.
Plus they don't trap the debris others do in the first place.
Ours are on and off. One machine the studs are snapped off so there's nothing to hold them on. Another machine we have them off of so the edge of the deck will get under board fence and our new machine we have them on.
On or Off depends on the machine.
On my '97 proline 30197, the belt likes to come off the spindles when it's disengaged and involves removing FIVE these *&%^ nuts every time the belt comes off (at least once/day), I got so tired of removing / re-installing the cover that it stays off because it really is better this way.
On the '05, the belt issue has been fixed and the cover only needs to come off about every 100 hours so I remove the cover maybe once/week, the blades can be swapped daily without removing it, only reason it comes off is to grease the one zirc under the deck cover plus it's a good time to clean it out and look at everything. This one stays ON, and the '97 WOULD stay on, I believe they should be ON but when you gotta remove the cover at least once/day, it's just too much.
But those stupid plastic cover bolts, they strip all the time and cost like 4 dollars each...You would think in 8 years or more of producing these machines, SOMEONE would've figured out what I did: Run to Lowe's or Home Depot and buy a slew of wing nuts and washers (you get like 8 or 10 for a couple dollars) and use those instead, I hate those stupid plastic spinner knobs.
In the end I agree, ON is better for not just safety but it helps keep dirt out and it just looks professional, too. Might make the machine more aerodynamic but the REAL plus I saw the day I went flying over the handlebars, it really sux to see spinning spindles and moving belts coming your way.