Personally, I love the tower shied and use it in all my builds. With a Tower Shield +5 and max stamina (endurance at 40), it's tougher than a rock to break. Combine that with a scraping spear, and you're in business.
Nothing is better than standing at that first walkway in 2-1, being invaded and watching a BP run at you full force 2 handing a cursed weapon enchanted Dragon Bone Smasher. 3 swings with the DBS on my TS+5, and not only have they not depleted my stamina enough to break my guard, I can get 2-3 pokes with the scraping spear in. And since the damage is purely physical, I take nothing. We both step back, let our stamina's reset, repeat. I always wind up winning that battle.
When it comes to TS+5 or PFS+10, it makes a world of difference only online. When you get invaded by a player with a magically enchanted weapon, the extra 30% magic reduction is huge. The only level that it might make a difference is in 3-1 and 3-2, when trying to block magical attacks. But if you're playing offline, then just switch to a dark silver shield with no worries of being invaded and having the wrong shield.
This is my build with a tower shield and it is HIGHLY effective:
SL 159
Vit: 60
Int: 18
End: 40
St: 30
Dx: 16
Ma: 18
Fth: 50
Luck: 7
Left hand 1: Tower Shiled+5
Left hand 2: Talisman of Beasts
Right hand 1: Blessed Long Sword+5
Right hand 2: Lava Bow (Scraping spear when invaded)
Ring 1: Regenerator's
Ring 2: Ring of Great strength:
Body armor: Gloom
Head, leg and arms: Black
Magic: Firestorm
Miracles: 2nd Chance, Banish
5 slots (99 of each): 1. New Moon Grass 2. Old Spice 3-5. soldier, royal & widow lotus
(plus I've reorganized my inventory to put ed's grindstone as the top item)
Arrows: Holy arrow
He doesn't hit that hard (340), but the longsword uses minimal stamina to swing, so I can get lots of swings for little damage. Plus, he regenerates 10 hp/sec, that's if you can get damage into him.