Pentax 300 or Sigma 70-200 f2.8 plus converter

I have another lens question.
As well as buying a new walk about lens, I'm going to buy a new telephoto to replace an Sigma 28-200 that I used with my MZ5. I'm torn between the Sigma 100-300 f4 or the new Sigma 70-200 f2.8 and a matched 1.4x Sigma converter. I'm not considering the new Pentax 300 f4 because of it's fixed focal length. I want the flexibilty of a zoom which is why I'm leaning towards the Sigma 70-200 with converter for ultimate flexibility.
However I'm open to suggestions and opinions. What do you think.Pentax

I don't have any of the two, but there is soon the new Da* 60-250 F4 from pentax. Might be worth it.

If it is as good as the 50-135 - it will be excellent.

Personally i would go with the f4 100-300mm and not bother with 1.4x unless you really want the extra reach. I may be mistaken but i think you lose AF with the teleconvertor : I know you do on the bigma and 180mm macro. I think this lens is the best compromise for a 300mm prime.

But as Nimitz says the DA*60-250 looks very tempting

I have the EX 100-300 f4 and 1.4x EX TC combo and it works fine...only with the 2x TC you 'lose' AF.

I also have the EX 70-200 f2.8... but the 100-300 is my preferred lens.

The Sigma 4.0/100-300 will auto focus with the 1.4 EX DG Converter.
When using the 2.0 EX DG Converter you will lose AF.
Probably the same goes for the EX 2.8/70-200.
Martin.

Edit, beat by a second