No doubt both are used, depending on circumstances.
Having done some recording in both styles (sequenced/synthesized and live-performance) even with my mediocre performance skills and low-quality hardware, I've still often found performing to be less-labor-intensive than sequencing (to my surprise). If you can find any random half-decent instrumentalist it doesn't take that long to stick them in a studio and have them run through a half dozen takes of a song.
That said, it may be the case that each instrumentalist is in their own separate sound-proof room, individually mic'ed, with headphones to monitor the others. This would give greater control to each individual instrumental track in post processing. There's a whole bunch of techniques you can do with a live recording to clean it up. This includes stitching together the best parts of multiple takes, adjusting the volume and panning envelopes, performing time-stretching (to correct misplaced timings) and pitch-correction (which isn't always an obvious autotune effect), adding EQ to emphasize or de-emphasize various frequency bands, adding artificial reverb or chorus effects, and lots more.
OTOH, it really depends on what is being recorded. For a guitar part, its probably easier to find someone to play the part live on a guitar rather than type it into a synthesizer or play a keyboard reduction into a MIDI sequencer. But if you're wanting a string pad, or some background orchestral parts, its certainly much easier and cheaper to play a synth than to rent an orchestra (or even a string quartet).
It's also worth pointing out the distinction between synthesized and sequenced. Synthesized music describes sounds that have been created digitally, but such music can be (and often is) still recorded from a live performance on a MIDI controller (such as a piano keyboard), and thus, in some cases, requires the same instrumental skills as playing an actual instrument. Some forms of synthesis even trigger a recorded sound of an actual instrument. Sequencing OTOH is a method of inputting notes by means other than a live, real-time performance.
The point of this distinction is to point out that saying a song is "more synthesized than recorded" is not a meaningful distinction. Synthesized performances are still recorded (as when recording a keyboard player). The opposite of recorded music would be sequenced, where notes are typed into the computer in some type of interface.