@kaiser What *exactly* is this for? Any recommendations need to be aligned with this: a high(er) R-value is useful if you are doing winter camping but if it’s summer only then one with a low R-value will be fine.
Are you using this with a sleeping bag or quilt?
Is pack size important?
Is weight important?
Two/three/four season?
For summer ultra-lightweight use I’ve a Klymit X-frame, it’s got zero insulation and is full of holes but it weighs 260g and provides some softening of the ground. For the rest of the year or normal touring I’ve an Exped Winterlite Synmat, weighs 400g and has an R-value of 5 – it’s comfy and warm.
Don’t go with mats that are thick but have no insulation, they will develop internal air movement through convection that will cool you down – they are basically Li-Los.