So, having played through KGV and bought the Monarch, here's my review of the King George V, the tier 7 RN tech tree BB.  For my review of Queen Elizabeth, the tier 6 RN BB, click here.   Note: I am on the high side of average, skill wise, but no unicum. Also, while I did consult numbers and stats, my reviews are primarily based on the feel of the ship and my performance in her. This is of course a limited sample size, and is affected by my playstyle (which is generally fairly aggressive leading to occasional overreaches and a low survival rate.) Your mileage may vary.   KGV was a difficult ship to click with at first. Queen Elizabeth was fairly easy to settle into once I realized how strong the AP was despite the good HE being the 'flavor' of the British line, and I played her much like I play my NorCar or Missouri, albeit much slower. King George V is much quirkier, and I had to unlearn what I'd learned from QE. As such, I was wildly inconsistent for the first dozen or so games before I settled into her. She's not armored enough to be terribly tanky, and she's undergunned compared to her peers.    Queen Elizabeth is one of two 15" gun-armed researchable BBs at her tier, compared to the 14" rifles of most others at tier 6. So she's punchier than a New Mexi or a Fuso. KGV, on the other hand, drops down to 14" rifles at a tier where everyone else has 15" or 16" guns, with the exception, of course, of Scharnhorst. This meant I really struggled to do consistent damage until I figured out how to use her guns.  KGV is stealthier, she's faster, and she reloads quicker than Queen Elizabeth (25 vs 30 seconds.) But because she's facing higher tier ships with thicker armor and has smaller guns, her AP wasn't nearly as effective. I struggled mightily with doing damage early on; I'd bust out a 70 or 80k game and then potato out with a 20 or 25k game. This changed once I equipped IFHE and switched to using HE most of the time,prioritizing cruisers as targets; over my last ten games I found it fairly easy to bust out 60-70k games consistently. IFHE meant I could lolcitadel many cruisers from any angle, and her high fire chance meant I could stack damage even on higher tier BBs with HE where I'd struggled to do any damage with AP. She seems to handle bottom tier better than her peers since she can still be a firestarter and still murder cruisers of any tier. 

Her guns turn far quicker than QEs, but unlike the QE, KGV's rear turret is very difficult to use while angled. QE's rear firing arcs were fantastic; I could use all 8 guns while staying tightly angled to the target. With KGV, you can still angle decently and use the rear turret, but it's a very narrow window. When dueling an enemy BB 1v1, probably better to just forget about the rear turret until you're very comfortable with your shiphandling of the KGV.  I found myself most effective when I could stick with a pack and rain HE on a mass of enemy ships, switching targets as I stacked fires.Her AA is mediocre at best, which is another reason to not get isolated; you're going to need a cruiser or a BB with stronger AA along for help. I struggled to shoot down anything. You won't kill more than 1 or 2 planes out of a squad before they drop bombs or torps, even with your fighter up.    How to play her? Play her like a mid-range Scharnhorst. Rain HE, murder cruisers and DDs, push when you can but she's a bit more fragile relative to her tier than QE is. She cannot survive focused fire for long. When top tier, you can play fairly aggressively and brawl; when bottom tier, stick back at midrange most of the time and take advantage of her good stealth to fade away and heal when needed.    Note: For captain skills, I used PM, EM, Vigilance, CE, and IFHE. Still figuring out the rest of my captain build. You really need a 14-point captain to play KGV in my opinion; I found that CE and IFHE are both very important. I ran steering gear mod for faster rudder shift and then the typical BB picks for the other three slots. I did skip straight to B hull with free-XP as I hate stock grinds.    Pros: 
Gunnery is accurate. I was wrecking DDs with snap shots consistently out to 10-12 km.
Faster turret traverse
High fire chance  and excellent HE pen make her a cruiser murderer. You can citadel every CL I faced with HE from seemingly any angle and citadel most CAs fairly consistently.
Speed enables ability to flex across map as needed.  Solid support BB, most comfortable at mid-range but able to mix it up when necessary. 

Rear turret much harder to use while angling than QE.
Takes damage quick when focused or unable to effectively angle. Rudder and engine especially seem fragile. Torps murder her. 
AA is borderline atrocious compared to Gneisenau (my other keeper t7 BB.)
  Final verdict: I loved her after two games, hated her after ten, but after the 32 games it took me to grind through her, she's a keeper. Welcome to my port, KGV.