Lightest warmest fleece out?

Yes, and you can climb Everest wearing silk and wool. But I don't mind spending an extra $30 on a garment that I wear 60 days per year if it has quantifiably better performance than the cheapest option and might keep me more comfortable / have a higher safety margin in bad conditions.

most of us here arent climbing everest

and realistically there isnt any meaningful "safety" margin between cheap fleece and the fancy polartec ones … and even if there was you would have to throw out all your old polartec powerdry now that the new powerdry HE is out to keep that "safety margin"

and i own ALOT of fleeces

safety lies in your skills and the proper application of gear … not something thats marginally lighter or better, unless you are truly pushing the human edge which most here arent

;)

I have some generic fleece jackets from walmart/target Sears, and the school sports teams. They are approximately the same thickness as my polar tech fleece jackets from lands end, ll bean, and Sears — but not nearly as warm feeling.

I also find the "standard" polar tech fleece to be a lot warmer than the polar tech grid fleece. But they do feel more clammy during high exertion activities. However, since sweated-out fleece drys within 5-10 minutes – it's something I can live with :)

Personally, I'd just look for a fleece that is thick enough to provide the amount of insulation (ie loft) that you need for the temperature and activity level you expect, and buy polar tech or an equivalent. If it feels plastic-y rather than soft, or feels non-dense — then it's not equivelent.

If you plan on using it without a wind shell, then you'll want something with enough density to prevent tons of heat loss in a breeze – but not so dense that that your sweat can't evaporate as you walk. I just put a piece of the jacket over my mouth and try to breath through it. You can tell right away how dense the fleece really is this way. Hey – maybe that's why they call it "breathability" :)

Ps: 200 weight fleece is the standard weight they make most spring/fall jackets out of. 100 weight fleece is the standard weight for expedition long johns. 300 weight fleece is thick stuff, and is what they make winter fleece jackets out of.

Personally, I'd skip 300 weight fleece. It takes up waaaaay too much room in your pack, and is way too warm for hiking in. Substitute a mid weight puffy instead. I got a synth puffy from target that is as warm as 300 weight fleece for $30. It just has generic poly fill insulation, but it's warm and packs small.

Also, 200 weight fleece is too warm for hiking in unless it's around 20-30 degrees. Most 1/4 zip "shirt-like" pull overs are 150 weight fleece and work better for hiking in 30-40 degree temps. An expedition base layer (100 weight fleece) is nicer for 40-50 degrees though.