Xen users - Jul 2012 - virt-install flags affect my hvm performance?

Hi.

 This is related to hvm.

 I have read virt-install man page, I had read that we have a lot of
flags, we can be very specific on how we build a hvm for win 2k3, 3k3,
etc.

 Now, is important to be very specific on what we want to build or
virt-install is smart enough to detect our dom-U OS we are building?

 Running this:

virt-install -n win8-1 -r 2048 -f /opt/win8/win8-disk.img -b eth0
--vnc --vnclisten=192.168.50.2 -v -c /opt/win8/win8.iso

or

virt-install -n win8-2 -r 2048 --hvm --vcpus=2 --cpuset=2-3 --disk
path=/opt/win8-2/win8-disk.img --os-type=windows --os-variant=win2k8
-b bridge0 --noautoconsole --vnc --vnclisten=192.168.50.107 -v --cdrom
/dev/dvdrw

is important?

Exist a way to know how we build or dom-U? or is not important?

Does the options we give to virt-install affect our domU daily
operation(Performance)?

Running Xen 4.1.2.

Thanks!!!