There are two, basic schools of preference on this:
- The merino wool aficionados, who swear by it.
- The synthetic fabric folks (like me) who swear by their choice as well.
People tend to be passionate about THEIR choice. But, it is a personal preference and an opinion. Bear that in mind.
Both camps have merit. My advice is to experiment BEFORE you go on Camino, then proceed with the solution that works best FOR YOU. Personally, as I itch when sweaty, and do not like feeling sweaty in any conditions, I prefer the synthetics, as they dry while walking. However, I accept that others will find the merino wool superior. C'est la vie! Enough about base layers...
As regards a fleece mid-layer, please know that there are several standard thicknesses of fleece. All function similarly, but the thicker varieties have more insulation capability. None are wind resistant. You need to add an outer layer for win protection.
The industry-standard Polartec fleece (the inventor of this recycled plastic product) comes in three weights of thicknesses, referred to as: Polartec 100, 200, or 300. GENERALLY the 200 and 300 level fleeces are available with hoods. The 100 level fleece is good as a sweater or pull replacement.
I have been a fan of Polartec since it was first invented some 30 years ago. You know it is made from recycled soft drink or water bottles?
Anyway, my decades of experience and use, both casually and in performance situations, like the Camino, resulted in my finding that, for active pursuits, like walking the Camino with a rucksack, the "best" solution" appears to be a Polartec 100 or 200 level fleece without a hood, and with a full-zip front. This provides the needed insulation with the least relative weight.
For example, here is a link to the Cabela's fleece jacket page (Cabela's is a huge outdoor sports supplier in the US):
http://www.cabelas.com/catalog/sear...e+jacket&searchTypeByFilter=TopRated&x=10&y=6
If you "drill down" on specific products, you will find the level of fleece mentioned in the description. For example, look at this item:
http://www.cabelas.com/product/colu...TopRated&x=10&y=6&Ntt=polar+tec+fleece+jacket
This Polartec jacket features 200 level fleece, without a hood, but with a full zip. I have one exactly like it, but from the North Face. It works just fine and it my "go to" mid-layer. The issue of hood, versus no hood, is again, a personal preference. There is no wrong answer. Personally, I prefer no hood, plus a ball cap, sun hat, and or a Buff worn as a skull cap. I am never cold, wet perhaps, but never cold.
I think you get the point. My only other advice in this regard is to consider what you will wear UNDER and OVER this fleece. Buy the correct sizes.
For example, If the fleece is a size MEDIUM, worn over a size medium base layer, make sure the outer layer is roomy enough (LARGE?) for movement. We do not want to go 'a sauntering' on the Camino looking like a sausage...
Try stuff on in advance if you can. Just as an FYI, I have also had luck finding fleece garments in factory outlet stores. Try it.
The fleece is intended as a middle layer, over the base layer and under a wind-proof, perhaps waterproof outer layer. A typical configuration would be a short or long sleeve base layer (merino wool or performance synthetic fiber), covered by the zip-up fleece, covered by a waterproof rain parka.
I also use an additional poncho. It serves as a rain-fly. Depending on the ambient weather and winds, I can remove the rain parka, and wear the poncho over the fleece. The fleece serves as a jacket or light coat in the evening, or on "rest-days."
I hope this helps.