I ran the benchmark 4 times, twice on my XP 64bit, 720 and 1080, and twice on my Windows 7 64bit, 720 and 1080.
FINAL FANTASY XIV: Heavensward Benchmark
Tested on: 5/8/2015 6:08:11 PM
Score: 6160
Average Frame Rate: 52.358
Performance: Very High
 -Easily capable of running the game. Should perform exceptionally well, even at higher resolutions.
Loading Times by Scene
  Scene #1	4.822 sec
  Scene #2	6.309 sec
  Scene #3	6.353 sec
  Scene #4	6.080 sec
  Scene #5	6.655 sec
  Scene #6	3.871 sec
Total Loading Time	34.093 sec
DAT:s20150508180811.dat
Screen Size: 1280x720
Screen Mode: Windowed
DirectX Version: 9
Graphics Presets: Maximum
General
-HDR Rendering: Enabled
-Wet Surface Effects: Enabled
-Occlusion Culling: Disabled
-LOD on Distant Objects: Disabled
-LOD Streaming: Disabled
-Real-time Reflections: High
-Edge Smoothing (Anti-aliasing): FXAA
-Transparent Lighting Quality: High
-Grass Quality: High
Shadows
-Self: Display
-Other NPCs: Display
Shadow Quality
-LOD on Shadows: Disabled
-Shadow Resolution: High - 2048p
-Shadow Cascading: Best
-Shadow Softening: Strong
Texture Detail
-Texture Filtering: Anisotropic
-Anisotropic Filtering: x16
Movement Physics
-Self: Full
-Other NPCs: Full
Effects
-Limb Darkening: Enabled
-Radial Blur: Enabled
-Screen Space Ambient Occlusion: Strong
-Glare: Normal
Cinematic Cutscenes
-Depth of Field: Enabled
System
Windows XP Professional x64 Edition (5.2, Build 3790) Service Pack 2 (3790.srv03_sp2_gdr.130306-1435)
AMD FX(tm)-8350 Eight-Core Processor 
8139.844MB
AMD Radeon HD 7900 Series 6.14.0010.7279
Benchmark results do not provide any guarantee FINAL FANTASY XIV: A Realm Reborn (Windows version) and FINAL FANTASY XIV: Heavensward (Windows version) will run on your system.
FINAL FANTASY XIV: Heavensward Official Website 
http://na.finalfantasyxiv.com/pr/
(C) 2010-2015 SQUARE ENIX CO., LTD. All Rights Reserved.
Share Results
Type 1
http://sqex.to/ffxiv_bench_na #FFXIV Score: 6160 1280x720 Maximum DX9 AMD FX(tm)-8350 Eight-Core Processor  AMD Radeon HD 7900 Series 
Type 2
http://sqex.to/ffxiv_bench_na #FFXIV Score: 6160 1280x720 Maximum DirectX9 Windowed AMD Radeon HD 7900 Series 
Type 3
http://sqex.to/ffxiv_bench_na #FFXIV 1280x720 Maximum DirectX9 Score: 6160 Very High 
Type 4
http://sqex.to/ffxiv_bench_na #FFXIV 1280x720 Maximum DirectX9 Windowed Score: 6160 
Full Results
FINAL FANTASY XIV: Heavensward Benchmark 
 Score: 6160 Very High 
 1280x720 Maximum DirectX9 Windowed 
 AMD FX(tm)-8350 Eight-Core Processor  
 AMD Radeon HD 7900 Series 
 
http://sqex.to/ffxiv_bench_na #FFXIV
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FINAL FANTASY XIV: Heavensward Benchmark
Tested on: 5/8/2015 5:39:15 PM
Score: 4233
Average Frame Rate: 33.242
Performance: High
 -Easily capable of running the game. Should perform well, even at higher resolutions.
Loading Times by Scene
  Scene #1	7.256 sec
  Scene #2	21.128 sec
  Scene #3	14.373 sec
  Scene #4	13.288 sec
  Scene #5	12.692 sec
  Scene #6	6.625 sec
Total Loading Time	75.363 sec
DAT:s20150508173915.dat
Screen Size: 1280x720
Screen Mode: Windowed
DirectX Version: 11
Graphics Presets: Preset  1
General
-Wet Surface Effects: Enabled
-Occlusion Culling: Disabled
-LOD on Distant Objects: Disabled
-Real-time Reflections: Highest Quality (DirectX 11 Only)
-Edge Smoothing (Anti-aliasing): FXAA
-Transparent Lighting Quality: High
-Grass Quality: High
-Background Tessellation: High Quality
-Water Tessellation: High Quality
Shadows
-Self: Display
-Other NPCs: Display
Shadow Quality
-LOD on Shadows: Disabled
-Shadow Resolution: High - 2048p
-Shadow Cascading: Best
-Shadow Softening: Strong
Texture Detail
-Texture Filtering: Anisotropic
-Anisotropic Filtering: x16
Movement Physics
-Self: Full
-Other NPCs: Full
Effects
-Limb Darkening: Enabled
-Radial Blur: Enabled
-Screen Space Ambient Occlusion: HBAO+: High Quality (DirectX 11 Only)
-Glare: Normal
Cinematic Cutscenes
-Depth of Field: Enabled
System
Windows 7 Professional 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.150316-1654)
AMD FX(tm)-8350 Eight-Core Processor 
8140.148MB
AMD Radeon R9 200 Series (VRAM 3051 MB) 8.17.0010.1333
Benchmark results do not provide any guarantee FINAL FANTASY XIV: A Realm Reborn (Windows version) and FINAL FANTASY XIV: Heavensward (Windows version) will run on your system.
FINAL FANTASY XIV: Heavensward Official Website 
http://na.finalfantasyxiv.com/pr/
(C) 2010-2015 SQUARE ENIX CO., LTD. All Rights Reserved.
Share Results
Type 1
http://sqex.to/ffxiv_bench_na #FFXIV Score: 4233 1280x720 Preset  1 DX11 AMD FX(tm)-8350 Eight-Core Processor  AMD Radeon R9 200 Series 
Type 2
http://sqex.to/ffxiv_bench_na #FFXIV Score: 4233 1280x720 Preset  1 DirectX11 Windowed AMD Radeon R9 200 Series 
Type 3
http://sqex.to/ffxiv_bench_na #FFXIV 1280x720 Preset  1 DirectX11 Score: 4233 High 
Type 4
http://sqex.to/ffxiv_bench_na #FFXIV 1280x720 Preset  1 DirectX11 Windowed Score: 4233 
Full Results
FINAL FANTASY XIV: Heavensward Benchmark 
 Score: 4233 High 
 1280x720 Preset  1 DirectX11 Windowed 
 AMD FX(tm)-8350 Eight-Core Processor  
 AMD Radeon R9 200 Series 
 
http://sqex.to/ffxiv_bench_na #FFXIV
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On XP 720 I got 6160, and on 1080 I got 6135, hardly any score difference.
But on Windows 7 on 720 I got 4233 and 1080 I got 4205, again, hardly any difference in score between 720 and 1080. I just don't understand why the score is so much worse on Windows 7 with DX11 over XP with DX9.