I've been watching "experts" in YouTube and they all seem to favour a tarp over a tent and I just don't get it. The size & weight of a tarp plus a hammock and the necessary cordage, surely equal or exceed the weight and size of a small tent. In my view a tent is much more comfortable. Can anybody enlighten me?

A Tent equates to 'Camping'

A Tarp equates to 'Bushcraft Survival Expertise'

A green OD or Camo Tarp equates to 'Specialist Military Bushcraft Survival Expertise'

Anyone can pitch a tent but only the survival experts can survive a miserabe night under a tarp.

Give Bear Grylls a map and compass and his survival show becomes a trekking and holiday destination TV guide..

You can use a tarp at a toga bush party.

Apples and oranges. Tarps can be very light (ex. silnylon) and easily staked out for a comfortable night in almost any weather. Hammocks (ex. hennessey hammock) can be strung almost anywhere and you can sleep very comfortably in alot of circumstances I'm told (although ensuring you have enough insulation below you can be a problem in colder weather). Hammocks also afford protection from insects that tarps do not (at least without added mosquito netting). Tents can provide most of it, bombproof comfort but at a cost in terms of weight. fwiw I've tried to split the difference, my favorite camping tent is the Double Rainbow tarptent by Henry Shires, it is light weight and provides room for 2 and plenty of room for one solo, and necessary mosquito protection where I live. There are those who will argue for their tarps and their hammocks and that's all fine, they are probably great for them, I like the compromise of the tarptent.

look at a commercial sleeping bag's rating, and you are looking at one inside a tent. The tent is equal to the outermost wind or rain barrier clothing.
A tarp can provide same, with more heat loss even if the wind doesn't change or natural features are available to increase efficiency. A tarp also affords a ready view of your surroundings. That's nice if you're filming a nature program or keeping an eye out for pagan biker gangs.
All systems require a piece of Mother Nature to secure the things; branches,ground,trees.There are places such as the tundra or slick rock where that can be problematical short of a mongolian yurt or bivy bag.
And time in deployment may be an issue.
The biggest issue however is simply preconceived ideas based on other's opinions that are mislabeled 'experience.'
Is Bear experienced? Yes, if breaking your neck is a reasonable way of doing things. But that's just my 'opinion' like using tarps v s tents.

My Hennessy hammock plus under-and-over quilts plus tarp and all accessories is pretty much an even weight and bulk tradeoff for my tent plus sleeping bag plus pad. What converted me wasn't the weight but the comfort. If you are a hammock type, a night of hanging is infinitely more comfortable than sleeping on the ground!

As others have mentioned, you definitely need an underquilt in a hammock to sleep toasty.

I've wondered about tent vs. tarp, too. I've used tents in car camping scenarios but recently got a used tarp. I'm interested in bicycle camping in warm to cool temps, in occasionally "buggy" landscapes. I'd like a tarp to work because it "seems" lighter, but being eaten alive by no-see-ums, mosquitoes and flies seems worth carrying a tent. I have a short two-nighter coming up and will see how the tarp works.

The Tarptent looks very promising. Have to save up a long time for one of the two-man ones.

I don't bother with a tent because it's too much weight and bulk. If I had to sleep on a frozen mountain slope in the midst of winter I'd sure bring a decent tent. For anything else, a tarp is more versatile and lighter, though admittedly not as warm per se.

Most of the time I actually sleep under my poncho. This is probably the most economical kind of "serious" outdoor shelter. I always carry my poncho as my primary rain gear so I might as well use it to make a shelter. It's really useful for that sort of thing.

Also, I find tents a bit claustrophobic (I prefer to be able to see what's going on around me) and too prone to damage. Way too easy to snag your tent on a stick or rock. Making a fire anywhere remotely close to a tent is a bad idea too, hot sparks will burn neat holes and turn your prized tent into Swiss cheese.

A tarp/poncho setup is somewhat more practical IME. If warmth is a consideration, you can make a lean-to with 3 sides closed and the 4th close to the fire. Very likely warmer than an ordinary tent. The smoke will also keep away mosquitoes, insects and whatnot better than anything else. BTW, Les Stroud does pretty much the same thing on most of his shows though he tends to make fire VERY close to the shelter. I tend to keep it slightly further away but still within reach.

YMMV.

I've camped using tarps, tents, or just a bedroll, and I can say that in pretty near every case I prefer a tent. The weight for a one or two man tent these days is nothing, and the comfort it affords over the other two options in most any environment is far superior. It would take at least a good four hours and plenty of raw material to build a survival shelter anything close to what a decent tent would afford me.

I have a leightweight 2 man tent and a silnylon/Eaglenest hammock set up. Both weigh about the same if I carry each full kit.

I will always prefer a tent for the simple reason that its generally faster to set up. Provides a greater variety of areas to set up, especially in the desert, and generally provides more shelter from mozzies and rain.

Plus I am a side sleeper and thats usually not as comfy in the hammock.