i recently had to look at that also. Toolfarm/Michele recently posted excellent article on subject comparing various methods.

http://www.toolfarm.com/blog/entry/upscale?utm_medium=email&utm_...+Upscaling+...&utm_source=YMLP&utm_term=in+depth+upscaling+video

Good luck.

Message-Id: <20130930171804.89259f98f291d771214680e8971719cb.725c8da6ff.wbe@email04.secureserver.net>
From: "Robert W. Walker" <robertw@walkersound.com>
Subject: SD to HD
Date: Mon, 30 Sep 2013 17:18:04 -0700

Just my luck.  I have to resurrect some old SD commercial footage and=0Aamo=
ng other things make it HD.  I know AE CC's imminent update is=0Asupposed t=
o have a vastly improved scaling feature - question is, does=0Aanyone know =
WHEN the update is releasing?  I have a deadline.=0A=0AIf the update is goi=
ng to be too late for this job, what is the=0Aconsensus on the next best al=
ternative?  Instant HD?=0A=0AThanks,=0A=0ARobert Walker=0ALos Angeles