In past editions, whenever playing a Paladin, I would always choose the classic sword and board for concept and flavor over a greatsword. The added AC also seemed preferable over doing a bit more damage, but for 5e I'm having a harder time deciding.
While I'm not a min/maxer by nature, it seems the Great Weapon Fighting option can deal much more damage compared to using a longsword and shield. Being able to reroll 1s and 2s is a massive benefit, but it's also compounded by the fact that a Great Sword does 2d6 damage allowing these re-rolls for BOTH damage dice. I believe this benefit is compounded even further by allowing you to re-roll 1s and 2s on all smite damage when applicable. Does this not make a Great Weapon Fighter grossly overpowered? Is the disparity between these 2 styles that much greater than in past editions?
I've also heard the reverse argument that having a shield is much more important in 5e compared to past editions, as hitting higher ACs is so much harder. (Even with advantage, the mid ACs statistically get hit more often than the high ACs when rolling two d20s). The fact that everything scales so much less and over many more levels would also more strongly necessitate a great defence/higher AC I would think.
Advice/opinions most welcome. Is Great Weapon Fighting broken to the point that Sword and Board is no longer a viable/competitive option or do you think both fighting styles are fairly balanced against each other?
I think that - at least if you play a paladin - both options are completely viable. Your huge damage spikes will come from smiting anyway. Personally, I plan to take the +1 AC fighting style and switch between longsword and shield or greatsword depending on the encounter and the loot I find. I will most likely start with longsword and shield. Since I'm going to play a dragonborn my combat strategy will revolve around hitting a good number of enemies with my dragon breath and then finishing them off with the longsword.
i think the lack of consensus means the options are balanced and that it comes down to personal preference.
The duelling fighting style is pretty strong too, and can be used with a shield. It's definitely a competitive option, particularly if you also take the shield feat later to make up for (presumably) weak dex saves.
Assuming Improved Divine Smite, It looks like the three main options for personal stat boost fighting styles are:
Defense- +3 AC,9 damage+ modifiers / attack
Duelist - +2 AC, 11 damage + modifiers / attack
Great Weapon - +0 AC, 13.583 damage + modifiers / attack
Keep in mind that Great Weapon Style would also make divine favor, elemental weapon, active uses of Divine Smite, and the various smite spells stronger by roughly 0.75~1 damage per die.
Great Weapon Style also benefits from critical hits, whereas Duelist does not, increasing the damage bonus of Great Weapon style by about 5%.
Using Duelist as the baseline,
Defense Style gives +1 AC for -2 damage / attack.
Great Weapon gives -2 AC for +2.6 damage / attack, but potentially up to about +11 damage per attack when smiting with elemental weapon.
Unless your character concept was all about dealing out maximum damage with minimal regard to personal defense, I'd be inclined to keep my shield on a Paladin. I'd probably go Duelist style myself. Great Weapon Style could certainly produce some impressive numbers when using bonus damage dice spells and Smite attacks, though, especially on critical hits.
There is also the DM factor to consider. In my 36+ years of experience, I've observed that DM's have a tendency to fudge attack rolls when they want to show off a nasty monster ability, or if they believe that a particular character isn't feeling threatened enough by a particular encounter. They do this all in the name of dramatic tension, of course, but the net result is that a large investment in your AC is not likely to pay off as much as it should. By contrast, DM's are less likely to fudge a monster's HP in order to keep the monster around for a few extra rounds. Accordingly, if you have a DM who likes to make rolls in secret, I would opt for the Great Weapon Fighting style, especially combined with at least 3 levels of barbarian in order to pick up damage resistance against all damage types except psychic. If you have a DM who likes to make rolls in the open, then sword-and-board with the Duelist fighting style is quite viable, particularly at low levels of play when the characters are very squishy.
Leugren wrote:
I haven't checked the spell list to thoroughly, but I wonder how much the ability to stick your holy symbol on your shield as a Focus will push Paladins and Clerics towards sword n' board styles
SpedGuy wrote:
Thoughts_My_Aim wrote:
Leugren wrote:
Leugren wrote:
It also depends on party composition. If there's already a great axe barbarian and a dual wield rogue, you may need to protect squishies.
Leugren wrote:
UnknownMourner wrote:
Leugren wrote:
crimfan07 wrote:
Leugren wrote:
I'd absolutely go with the duelist style and fight sword and board. That +2 AC is worth more (on average) than the extra damage. The +2 damage that duelist gives you prevents you from falling too terribly behind the great weapon fighter. Now, would I take the defensive style for a +1 AC (total +3 counting shield)? Probably not. The defense style is probably most effective as a champion fighters additional fighting style at 10th level, rather than anyone's choice as a single fighting style.
Great information here for making a better informed choice. Thanks guys. 
2Chlorobutanal wrote:
Sword_of_Spirit wrote:
Angel7 wrote:
crimfan07 wrote:
MBTL90 wrote:
crimfan07 wrote:
Thoughts_My_Aim wrote: