Question 64 or 32 bit LL 2.2 Opinions welcomed

[newtusmaximus]

Have  a 2007 ultra slim desktop HP Compaq dc7700 which currently has 3 x 1 GB Ram fitted  running on 32 bit  LL2.0
RAM  usually only 10% occupied.  Bios previously updated 2011 version.

System apparently has 64 bit capability so out of interest ran live LL2.2 from USB and all appears to be working OK.

Question therefore:-

What would be the advantage of running 64 bit instead of 32 bit given that existing  RAM is only 3GB and barely occupied.  To fully utilise the 64 bit capability the dc7700 will accept 3 x 2gb RAM modules. Not a cheap upgrade £65.00 or so

Bearing in mind the desktop PC is being used for "normal" office use NOT CAD,  Intense Graphics ( photo editing) or gaming.  is there any point in changing from 32bit to the 64 bit option; with or without RAM upgrade?  Thanks