A few questions that need to be asked when choosing a smoother:
(1) What type of wood do you expect to use the plane on - straight grained and undemanding, or interlinked and complex grained?
For the former, you can use just about anything, and standard, 45 degree angles of attack will work as well as 60 degree, high cutting angled planes.
For the latter, only a high angle of attack is recommended. While this is not the only feature that decides how well a plane will smooth this type of wood, it is a dominant feature.
(2) Do you prefer the feel of a high centre of effort (BD design), or that of a low centre of effort (BU design)?
(3) Are you interested in a wooden- or a metal bodies plane? If the former, is it essential that you have a mechanical blade adjuster (such as a Norris-type adjuster), or are you comfortable using, or learning to use, a mallet to set a blade?
Choosing the "best" smoother is often a meaningless task. If all the variables are held equal then the differences in performance may be down to the sharpness of a blade, the amount of blade projection, the size of the mouth, or the way the wind is blowing. That is not to say that all smoothers are equal. Far from it. Some are better suited to certain wood types. A lot depends on the skill of the user. It may, in the end, come down to "feel".
On really hardwoods I much prefer a heavy plane. My favourite then is a Marcou S15.
OK, these cost a fortune, so inclusion here is just to make a point.
Running a damn close second to the Marcou is the LV BUS. For its price it is phenomenal. It is large but not as massy as others. I have rehandled mine.
A smaller, more versatile version of the BUS is the LV LAS. This has less untimate control and stability as it has lower mass, but it provides greater feedback ("feel") and is also a superb plane on a shooting board. Again mine is rehandled.
Larger BD smoothers, such as the LN #4 1/2 are equally terrific planes. I would choose one with a high angle frog for the timber I plane, and they are now available in 45, 50 and 55 degrees. Early this year I received the bronze Anniversary model from my wife with the 50 degree frog. It performs superbly, but I must admit to preferring the BUS with regard feel.
Some of my favourite planes are my woodies. Among these the HNT Gordon Smoother is the one I grab first. It is low slung, high angle, and has a slippery slide along the wooden surface.
These are all special planes, ones that anyone would be happy to own and use. None are perfect but all work well within their envelope.
Happy decision-making!
Regards from Perth
Derek