Let’s break it down. What does Large get you, just by itself?

“Neutral” elements:

• You take up a 2×2 area instead of a 1×1

Benefits:

• You’d probably get Reach:2 with your melee attacks (your threatening reach would only be 1 square out, though — so no Reach 2 opportunity attacks — but since the “ring” of squares around a 2×2 creature is 4×4, not 3×3, you would be threatening more squares due to having more adjacent squares).
• You should be using one-size-boosted weapons — which would increase the die size of any weapon you use, as per PHB page 220. This essentially amounts to “+1 damage with all melee weapons”.
• Also as per PHB 220, you’d be able to use two-handed weapons of Medium size class in one hand, but you simply can’t use one-handed weapons of Medium size because they’re too damn small.
• Your “Close Burst” powers essentially cover a greater area (at least the way I imagine them working — though you could patch this by saying you have to choose one of your four occupied squares as the square of origin, which would mean that a close burst 1 would be partially swallowed by your occupied squares).
• You can’t be Bull Rushed by Small or smaller creatures — so halflings and other Small races wouldn’t have that tactical option against you. Flip that around, and it would mean that you *can* bull rush something that’s Huge!
• For your allies, you’ll be providing greater cover (allies provide cover to one another), but little obstruction (see below).  For your enemies, you’ll be a formidable obstacle, able to singlehandedly block a 10-foot-wide hallway (they just won’t be able to move through you) — and with your opportunity attacks going one square out to either side, you could “cover” a 20-foot-wide opening (a Medium sized creature would cover 15 feet, so this is just a 1 square gain).

Downsides:

• Fitting into places is tough, but at Large, it’s not impossible. See PHB 292; the Squeeze action is the key. You can still fit into that room that’s less than 2 squares high or through that doorway that’s only 1 square wide — but you’ll move only half your speed, take a -5 penalty to attack rolls, grant combat advantage, and provoke opportunity attacks when you do so. Those are some significant downsides, but so long as you’re not getting regularly hosed by it, it’s managable — most often, you’ll
• It would be harder to gain superior cover. It just plain takes something larger to give you superior cover — if it doesn’t span at least two squares (horizontally and vertically, I would imagine), it can’t provide it.
• The enemy can mob you more effectively.  There are 16 squares instead of 9 they could use to surround you, and from opposing “flat sides” to the 2×2 square you occupy, being in either of the two squares on each side yields flanking.
• Minor hassle: because you take up 4 squares instead of 1, 2 across at any point, while your allies can move through your squares at no penalty, they can’t stop in those squares, so getting past or behind you will take just a little extra work on occasion.
• If you’re in a game that tracks gold usage, larger weapons and items should just plain cost more.

Looking at all of this, factoring in the downsides, I’d say being Large is at least as awesome as having Dragon Breath.  Using my rule of feat-equivalence in Hard Boiled Cultures, Dragon Breath brings several benefits to the table: it allows an attack as a minor action, and it affects an area, making it the equivalent of three feats.

Here, we’re seeing: Reach 2 on melee. That’s at least one tick-mark.  The +1 average damage due to an upsized weapon is really one side of the same coin as being able to wield a medium two-handed weapon in one hand.  Call those another tick-mark.  The other benefits of being greater in size get another 1-2 tick-marks.  So all in all, I’d rate being Large as being the equal of at least 4 feats — one more than dragon breath.

The Dragonborn are an interesting baseline to compare this “PC Giant” to, then.  They have the standard 6 speed, 2 languages, +2 to 2 traits (Strength and Charisma would make a good pairing for a Giant PC, too), 6 speed, +2 to 2 skills (for a giant, I’d probably go +2 Intimidate, +2 Endurance), and two racial benefits beyond their dragon breath.

Swap out for a Giant PC, and you’d have only 1 racial benefit beyond that core if I’m correct in valuing Being Large as being 1 feat-equivalent more than dragon breath.  My short-list for that one remaining racial benefit is either a Speed of 7 (greater stride — and certainly appropriate, given that the Monster Manual’s hill giants have a speed of 8), a boost to Fortitude defense (+2, perhaps), or the equivalent of the Toughness feat (more size equals more HP).

Have I missed anything in my assessment here? Is “4 benefits” the correct valuation for Being Large, given the downsides?  Is playing a Large PC viable at all, for your games & experience?

Talk to me.

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