[snow white]

Last year I experimented.  I had sweet millions cherry toms and Alicante toms.  I grew them corden in the pt and left them alone outside in a bed.  They both produced lots of lovely toms.  The greenhouse ones were red earlier easy to pick and were perfect.  The left alone ones, bent under the weight of the fruits and needed some support, so I put canes on some of the stems.  They took longer to ripen and towards the end they all got blight.  So if they need treating as a cordon, there is usually a reason. 

[Growster...]

I'm growing Marmande this year too, and expect to cordon them like the others.

[Headgardener22]

Last year I experimented.  I had sweet millions cherry toms and Alicante toms.  I grew them corden in the pt and left them alone outside in a bed.  They both produced lots of lovely toms.  The greenhouse ones were red earlier easy to pick and were perfect.  The left alone ones, bent under the weight of the fruits and needed some support, so I put canes on some of the stems.  They took longer to ripen and towards the end they all got blight.  So if they need treating as a cordon, there is usually a reason.

This lines up with my comment and experience, the only thing I haven't tried is letting an indeterminate variety run rampant in the polytunnel (there isn't space) but I might have a go this year. I would suggest that the fact that your plants got blight last year is nothing to do with whether they were grown as a cordon or not, my outdoor plants almost always get blight (all varieties, however treated) because its in the atmosphere and brought down by the rain, that's why I've basically given up growing tomatoes outdoors except for my excess plants.

[RJR_38]

Last year was my first and we obviously had a very good summer so the fact I got an excess of outdoor cherry size tomatoes may not happen every year so a bit if an experiment this year!