Which is the best choice, pae or x64?

[Rofail Qu]

My PC is x86 arch and has 4GB of mem.
I tried,
$ cat /proc/cpuinfo |grep lm
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat
pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc
pebs bts pni dtes64 monitor ds_cpl cid xtpr lahf_lm
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat
pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc
pebs bts pni dtes64 monitor ds_cpl cid xtpr lahf_lm

So, i think it support x64 as well.
The question is, which kernel should i choose? The pae or x64?
Which is the best choice? Why?
Thanks.