Halogens are MORE efficient than LEDs in selected parts of the IR spectrum if the selected portion is wide enough. It deep-ends how wide a slice of spectrum you want to consider useful.
For narrow bandwidths LEDs are better.
In whole visible range LED is much better than halogen as halogen has much more IR out than visible out.
Halogen is 100% efficient overall as ALL energy in comes out as light and "heat".
A GOOD modern (narrow band) LED at one wavelength puts out 1/3 to 1/2 of energy-in as wavelength-out. The rest goes to heatsink as widish band heat.
If the heatsink IR out is not useful in your application it is lost to you.
IF the LED heatsink IR is useful to you then it too is 100% efficient.
Odds are you do not want the LED's heatsink IR.
As you narrow the halogen bandwidth you use you use less of total output and "useful efficiency falls". When you drop under 1/3 to 1/2 of total energy in bandwidth you consider useful then LED is more efficient.
eg when using a halogen for optical lighting we consider a bandwidth that contains about 5% to 10% of the total energy out to be useful. So a modern LED is always more efficient for lighting at its design wavelength than a halogen is and more efficient in the whole optical band (all energy summed) than a halogen is.
If we use a halogen bulb to illuminate a typical silicon solar panel we find its efficiency RISES as a portion of the IR output falls in the panel's response range.
An (apparently) excellent reference: A major problem in trying to do useful things in this field is that, as in most areas involving people + healing / health / therapy / well being / feel good ... there is an immense amount of hype, hearsay, suspect claims, bad science and general rubbish to wade through. That is not to say that there are not very real and demonstrable benefits available - just that sorting the (w)heat from the chaff can be difficult.
This reference LED Light Therapy provides 29 pages of comment, reported results, and comments on investigations. It's not perfect, but at a quick glance it looks better than much that can be found. And it will probably address the OP's less than fully specified question better than any answer here can do. While the title suggests it's about LEDs it also deals well with halogen light use.
It may be educational to examine the sites usage of terms such as IR, heat and wavelength. Maybe not :-).