I've been trying to find "the best" way to wire a 3PDT, and I've come across several different methods.
On this one, http://www.beavisaudio.com/techpages/StompboxWiring/StompboxWiring_SwitchcraftJacks.gif , the output jack tip is tied to two poles on the 3PDT.
But on this one, http://www.beavisaudio.com/techpages/StompboxWiring/ , also from Beavis, it's not.
This one looks the most logical to me: http://www.tdpri.com/forum/attachments/burnt-fingers-diy-effects/158546d1356793958-3pdt-foot-switch-wiring-many-different-ways-forumrunner_20121229_091235-jpg
This one, http://1.bp.blogspot.com/-k5Sh68yVU18/TzGRFKbiALI/AAAAAAAAAlk/CbfaaduUjYQ/s320/%21Offboard+wiring.png , grounds 3 poles.
LED can go to battery snap positive or to V+ on the board.
One even has the red battery lead going to the switch.
Does any of this matter? Is it really "To each his own"?
http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b/
Nice, neat illustrations. Does not have to be a 1590b of course.
This one, on Joe Gore's Tonefiend website, is the diagram that made it all make sense to me:
(http://tonefiend.com/wp-content/uploads/BoxingDiagram.jpg)
Once I started using this diagram, my success-to-failure ratio improved.
I use the one from the TPDI site foor the reason you mentioned. You can connect the circuit input lug with the bottom centre lug to ground the circuit when it's not engaged.
There are two things I look for in a wiring diagram.
1) Grounded input. Does the input of the effect get grounded when bypassed? Not every circuit need it, but better safe than sorry.
2) Separation of input and output wires. Pedals with more gain can do bad things when the input and output wires are near each other. I like have the left and right lug banks of the switch deal with audio switching and the middle for LED.
This is the way I do it.
(http://img.photobucket.com/albums/v494/CodeMonk/Builds/Stomp_Switch_Wiringpng_zps12e1bf56.gif) (http://smg.photobucket.com/user/CodeMonk/media/Builds/Stomp_Switch_Wiringpng_zps12e1bf56.gif.html)
I do it the same as CodeMonk, though sometimes I don't ground input during bypass (mostly if it's not a higher gain pedal). The method he posted helps with switch pop I've noticed as well.
I've started to ground the input when bypassed - my Simple Parametric (geofex) powers up in oscillation if I've left the Q quite narrow.
Instead of the input sometimes I have also used that unused switch contact to ground a pin on a 567 or maybe a 555 in a noisemaker. Mind that you don't draw any current by grounding the wrong thing.
There are functionally only 4 different ways to do it (at least I can't think of a fifth):
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=47646) (http://www.aronnelson.com/gallery/main.php/v/diyuser/GGBB/3PDTWiring.png.html)
But mechanically/physically there are many variations. CodeMonk's is the input grounding variation - and I think that's what most of use DIYers tend to do. I came up with a variation of it a while back that I use now because it keeps all the wire connections on the outside lugs (I use component lead for the small jumpers on the inside lugs):
(http://i1190.photobucket.com/albums/z460/GGBB1/Miscellaneous/3PDTWiring-6_zpse54a4f43.png~original) (http://s1190.photobucket.com/user/GGBB1/media/Miscellaneous/3PDTWiring-6_zpse54a4f43.png.html)
Whenever I see the last one the OP linked (http://1.bp.blogspot.com/-k5Sh68yVU18/TzGRFKbiALI/AAAAAAAAAlk/CbfaaduUjYQ/s320/!Offboard+wiring.png), I like to point out the uselessness of connecting the lower left lug to the two adjacent lugs - it is completely redundant, requires more work, uses more solder (and wire), and creates more opportunity to damage the switch from soldering heat.