Recently bought a 38' Present/Nautique. About 21,000lbs and with the fly bridge and radar arch about 17' tall. Came with a 45lb CQR. .....Seems with the windage on the new boat a bigger anchor would be called for. Plan is all chain rode.
Bob
Eric Henning called it correctly, I think, and that is that the answer to your question lies in the type(s) of bottoms you'll be anchoring in. Anchor tests, while they can be spun to make a particular type of anchor outshine others, do provide good comparison data if you look at enough of them. You'll start to see patterns emerging. Like for sand and mud bottoms, the Danforth-type seems to always be at or near the top in terms of holding power. And claw anchors (Bruce, etc) do very well at intial setting in a variety of bottoms but are at or near the bottom of the list when it comes to holding power. And so on.
The advice to look at what other boaters in your area are using and get that is good up to a point, but when it comes to anchors boaters tend to be a bit like sheep in this regard. They get what other people have because other people have them. It's one of the main reasons we changed the Danforth-type anchor that came with our boat (from SFO Bay where that anchor type is an excellent choice) to a Bruce. Bruce/claw and CQR are still the most numerous anchor types in this area.
But you have to take into consideration that these days I would say the majority if not the vast majority of boaters never use their anchors. Or use them only as lunch hooks in a protected bay. So the fact that every other boat in the marina has a Bruce or CQR or Danforth does not mean that all these boaters are experiencing outstanding performance from them. It just means these anchors have become the anchors of choice for boaters to stick on their bows.
For us (and others we know) the Bruce proved to be a very "draggy" anchor despite its fast initial setting. So we eventually got rid of it and went to a different type.
Forty five pounds seems a good size for a 38 foot boat under "normal" anchoring conditions. Of course, defining "normal" is a sort of frustrating exercise. Personally, if someone held a gun to my head and said I had to use a CQR or a Bruce on a 38' powerboat I would go at least one if not two sizes larger than 45 pounds if the pulpit and windlass could accommodate it.
However, for the area we boat in and knowing what I know now I would not choose either a CQR or a Bruce/claw anchor for any boat we owned. Like Peter B above, I believe there are far superior anchor designs out there today and would go with one of them.
For our waters and our conditions (PNW) I believe all-chain rode is superior to a combination rode unless the boat is very weight-sensitive in the bow.