There are three goals when draining a tank:
1. Remove all water for long term storage to prevent "stinky" water or for winterizing.
2. Flush the tank. Even with the best filtration systems for the water supply calcium deposits will seem to form. I don't know if an additional (portable) water softener in addition to the filters will solve this, but I don't have one and I find calcium deposits in my RV's water heater. I use a WH wand to clean out the tank.
3. Check the condition of anode rod, if equipped. The anode rod collects all the impurities to protect the WH walls and it will eventually corrode. As this happens the corroded material drops to the bottom of the tank which is why if you wonder where the parts of the anode fall off, where do they go? The bottom of the tank.
Using a petcock only helps with #1. If you want to use a petcock you'll still need to perform items #2 & #3. Since I went to the trouble of getting the tools, I remove the plug/anode to drain the tank (don't forget to step to the side) and flush it out with one of those wands. Then I replace the plug and next trip DON'T forget to wait until the hot water tank fills up before turning on the heat.
If you use a petcock, the extension tube to the ground would help and eliminate the mess (and slow the draining down). Since I don't use this, I use a couple of 5 gallon buckets (on a furniture dolly) to drain into. There's still a mess but I catch most water, then put that water on the plants. I put both buckets on the dolly to make it easier to switch the buckets after the first one fills up.