Pentax 150 450mm f 4 5 5 6 vs tamron 70 300mm f 4 5 6?

Here is what the site says about that.

From Pentax HD D FA 150-450mm f/4.5-5.6 ED DC AW: Pentax HD D FA 150-450mm f/4.5-5.6 ED DC AW: A zoom lens by Pentax for Full frame cameras, 150-450mm f/4.5-5.6.

From Pentax HD D FA 150-450mm f/4.5-5.6 ED DC AW: What it frames like: - On full frame (Pentax K): as marked, 150-450mm. - On APS-C (Pentax K): like 225-675mm on full frame; f/4.5-5.6 gives about the depth of field of f/6.8-8.4 there.

Quoted from this site's pages.