diffrences between gmod 9 and gmod 13?

what is the difrence between gmod 9 and 13?

also will this run gmod 13? I can run gmod 9 fine.

OS Name Microsoft Windows 7 Home Premium
Version 6.1.7601 Service Pack 1 Build 7601
Other OS Description Not Available
OS Manufacturer Microsoft Corporation
System Name BRENDAN-PC
System Manufacturer TOSHIBA
System Model Satellite C650D
System Type x64-based PC
Processor AMD E-300 APU with Radeon™ HD Graphics, 1300 Mhz, 2 Core(s), 2 Logical Processor(s)
BIOS Version/Date Insyde Corp. 1.60, 6/23/2011
SMBIOS Version 2.7
Windows Directory C:\windows
System Directory C:\windows\system32
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = “6.1.7601.17514”
User Name Brendan-PC\Brendan
Time Zone Eastern Standard Time
Installed Physical Memory (RAM) 3.00 GB
Total Physical Memory 2.60 GB
Available Physical Memory 873 MB
Total Virtual Memory 5.20 GB
Available Virtual Memory 2.75 GB
Page File Space 2.60 GB
Page File C:\pagefile.sys

There are too many differences to post here, I would check out garrysmod.com
I think Garry has some change-logs posted there.

Performance should be similar to Gmod9, however it is going to require a little more to run with all the settings maxed. But honestly you should be fine.