Compare laptops

Can someone give me a breakdown between http://www.ozbargain.com.au/node/26964 and http://www.ozbargain.com.au/node/26690

So the

• CPU - Intel Core i7 720QM Processor (1.60GHz)
• Chipset - Intel HM55
• Display Panel - 16 LED Display
• Standard Memory - 4GB DDR3 1066 (2G x 2)
• Hard Drive - 640GB HDD 5400rpm
• Optical - DVD-Super
• NetworkingWireless - bgn
• Graphics - ATI HD5730M 1GB
• Bluetooth - Yes
• Operating System - Microsoft Windows 7 Home Premium 64Bit
• Battery - 6 cells battery
• WARRANTY - 2 year warranty

and

Dell Vostro 3700 $1,359 ($340 off)

• Intel Core i7-720QM (1.6GHz Quad core)
• Windows 7 Pro 64bit
• 4GB DDR3
• 500GB HDD
• 17.3 LED Display (1600x900)
• GeForce GT 330M 1GB
• 8X DVD +/- RW

And also, who would need 6 gb of ram?