MSM or 'old way' - Which to choose in this scenario?

Question

I'm about to create a new site with a 2-3 year lifespan. The new site will run off an existing EE2 installation which already runs two MSM sites. After 2-3 years, the site will be taken offline and new site with a 2-3 year lifespan will replace it.

• The data model of content for the new site will be sufficiently similar to content on MSM site1 not to warrant new channels and fields (I feel).
• In addition some content from site1 will be displayed on the new site.
• MSM license allows for up to 3 sites; additional sites are purchased separately

Given this and the 2-3yr lifespan, my thinking is to create the new site using the 'old way' and not using MSM. Then display the appropriate content via a tag, custom field, or category based filter.

Is this logical? Am I missing any "gotchas"?

My other thought was to create a sufficiently generic new MSM site which I could re-purpose every 2-3 years. Is this a better option?

---

Edit: The 'old way' is a means of running more than one domain from an EE installation without using MSM (the Multiple Site Manager add-on for EE). It involves creating and modifying an 'index.php' file at the web root of your new domain. Prior to EE2 and MSM this was documented on the official EE wiki, but it is no longer officially supported. For exact details see, for example, this post: "Old-Style" multiple sites on one installation

Answer 1

If the site will go offline before being replaced with new one, I would choose MSM approach. You will not need extra licenses (as old site will be removed) and it is easier to manage than "old-style".

Answer 2

I tend to use MSM when the content is significantly different, but the 'old style' method for when sub-sites or shared sites have very similar content. It's pretty easy to set-up, I generally just add a field called 'subsite' which matches the info in admin.php, then use in field search.