Right now I have 15lb spiderwire spooled on my Pfluger Trion and its been working fine for the past few weeks (I mainly fish for small bass, bluegill, and crappie). I've been reading a few form posts that say the maximum braid size should be 10lb test... I have no reason to not switch to 10lb braid apart from cost. So should I stick to 15lb braid or make the switch to 10lb? It should also be noted I fish a 6lb mono leader most of the time (4lb if fishing clear water).

Doesnt matter

As long as you don't overtax your equipment, you're okay using what you have. If it ain't broke, don't fix it. 

I would keep the 15 because it's a little tougher than 10lb and isn't that much bigger in diameter

 

i also have 15lb braid on my panfish setup, but usually go with 8 lb mono for leader if I am using one 

15# is fine for just all around use, say 1/8 oz and up. However, if you start downsizing and throwing 1/16, 1/32 or 1/64 oz baits instead of your normal stuff, lighter line will perform much better. I personally use 3#, 5#, and 8#  braid for all my lighter stuff with 4, 6 or 8 pound leaders.

 

-T9

I throw lures ranging from 1/32 to 1/8 

Simply saying lighter pound test will work better with lighter weight lures in most cases, but if you're catching fish and happy, then keep rolling with what you're doing.

I go with 10, but am considering lighter for summer fishing.  Braid is strong stuff, that said if your looking for universal fishing there is little downside to 15

I'd just keep using the 15lb you have. you have the option to put on a 2-4-6lb leader which is most important.  yes you might gain some casting distance with 10lb or even 5lb but to me the losses far outweigh the gains.  i put 5lb on my crappie/trout rod and it's been a disaster.  i mainly cast with it so i'm continually encountering timber, rocks, docks etc.  Cover severely compromises light braid.  I've broken off multiple nice bass and it snaps like butter when even trying to unsnag a light wire crappie jig.  imo 3-5lb braid should only be used for vertical jigging in open water where you won't get any abrasions.  15lb braid will keep a smile on you face when you hook into a bigger multi species fish.  vs the look of sorrow and defeat from light braid snapping.  i currently have some 10lb on rods but when it's gone I will only fish 15lb+.

 

Even when crappie/trout fishing I'd still like my equipment to be able to land a 5lb bass, 10lb catfish or 20lb carp. i guess that means my 'ultralight' set up is modified a bit.

Your definition of ultra light and mine are a bit different. 15 lb line is what I used to use for big pike. For lures as light as you are using, I'd be using 4-6 lb line with no leaders needed. Panfish have never shown me to be line shy.  They'll certainly cast much better with light line. If 15 is what you have, go ahead and use it. 

25 minutes ago, ClackerBuzz said:

I'd just keep using the 15lb you have. you have the option to put on a 2-4-6lb leader which is most important.  yes you might gain some casting distance with 10lb or even 5lb but to me the losses far outweigh the gains.  i put 5lb on my crappie/trout rod and it's been a disaster.  i mainly cast with it so i'm continually encountering timber, rocks, docks etc.  Cover severely compromises light braid.  I've broken off multiple nice bass and it snaps like butter when even trying to unsnag a light wire crappie jig.  imo 3-5lb braid should only be used for vertical jigging in open water where you won't get any abrasions.  15lb braid will keep a smile on you face when you hook into a bigger multi species fish.  vs the look of sorrow and defeat from light braid snapping.  i currently have some 10lb on rods but when it's gone I will only fish 15lb+.

 

Even when crappie/trout fishing I'd still like my equipment to be able to land a 5lb bass, 10lb catfish or 20lb carp. i guess that means my 'ultralight' set up is modified a bit.

 

Not sure what you're doing wrong, 'cause I'd like to help you out. My experience has been 180 degrees opposite of yours with lighter braid (why I use it so much). I've landed 50# grass carp, 40# buffalo, along with low teens channel cats and wipers on nothing heavier than 8# braid and/or leaders, with 5# getting the majority of use. I don't intentionally go looking for fights in heavy cover, but I'm not scared of what a fish might do based on what I've been able to land.