
Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

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As far as $/warmth ratio, this one is the winner. $50+ cheaper than S2S, Therma, Nemo and really comfy. I love mine.
The 3R is a pretty incredibly value for an 18oz pad at around $150. The 5R is probably better for being in Maine outside of summer.
Exped Synmat Ultra 3R. The comfiest pad for side sleeping that I have ever found, and it doesn't make the awful crinkly noise like some other mats (e.g. thermarest) do. Its pretty robust too. If you want a higher R value, they go upwards in model number - e.g Ultra 5 or 7, but the Ultra 3 is perfect for 3 seasons.
This is what I use and love it.
No one in ultralight group odd going to recommend extra weight for a little comfort. I use a switchback and exped inflatable and think it’s great for all the reasons you list. Added r value, backup pad for some comfort incase exped gets leak, foam pad protects pad, etc. is better comfort, but not ultralight.
This is the pad that finally let me sleep
+1 for this pad. I find it to be extremely comfortable and it comes with the best inflation sack on the market…doubles as a waterproof pack liner.
From your post history you seem to be based in the Netherlands. What is your budget? Hikingsite has a second hand market with currenty a nice offer for a used exped 3R wide model. A comfortable and light mat, good for summer. And I'm going to put a new unused Ether Light XR mummy on marktplaats for 120 euro (instead of 165). Good 3 season option, comfortable, light, small pack size. Let me know if that's something for you, I'm not in a hurry to sell it.

Exped
MegaMat Series
Car camping comfort champ, but some side sleepers find it thin.

Exped
Ultra Series
Lightweight side-sleeper comfort, but a bit pricey and bulky.

NEMO
Tensor Series
Ultralight side-sleeper comfort, but slippery and prone to leaks.

Big Agnes
Rapide SL Insulated Sleeping Pad
Comfortable with side rails, but heavy and warmth claims disputed.

Therm-a-Rest
NeoLoft™ Sleeping Pad
Very comfortable, good service, but heavy and bulky for backpacking.

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Exped - MegaMat Series

Ranked #1
Therm-a-Rest - NeoAir Xtherm Series