There is a lot of good info on sdr on line.
All the methods can work very well, the devel is in the details.
Direct sampling generaly means the rf is sent to a A/D converter and digitized and then processed.
It has the advantage of being able to look at and listen to multi bands at the same time, like 160 40 and 10 meters at the same time.
Or, to improve performance it can go through a band pass filter.
The Anan and Flex radios (and the new K4 from Elecraft do this.
The Elad fdm duo did it also, along with the QS1R and the Persious.
The number of bits in a sample, 12, 14, 16 improves the dynamic range as you go up in bits.
Then there is downconverted, the RF is mixed down to something like 8 MHz, put into a filter and then digitized and processed. The new FTdx 101 and 10 do that.
The original method was to downconvert rf to audio, digitize it into I and Q and then process it.
That method can still work quite well.
The Flex 3000 and 5000 did that, and many other radios.
There seems to be two ways to get very good close strong signal rejection, digitizing into more bits or filtering out the strong unwanted signals by downconverting and using a good analog filter to limit what gets to the A/D converter.
A lower frequency (8 MHz) can also use a cheaper A/D converter with more bits.
From what I understand, you have to sample the highest frequency you want to process at least 2X that frequency, so at 60 MHz you need to sample at at least 120 MHz.
All the above may be right, or sort of, just what I get from reading stuff since SDR came out.