it's apples and oranges, at a certain point.
First, the 424mkIII is a full 6-channel mixer, plus more stripped inputs, and that's clearly more than the 244's 4-basic channels. This offers a slightly higher production value on the front-end-mix side of the equation than the 244, by advantage of having 6 fully equipped channels.
Second, the 424mkIII's record-assign switch matrix enables the 424mkIII to record either 2-simul in Bus mode, or 1-4 tracks in direct mode, which is a slight cut above the 2-bus or all-4-direct switching assign matrix of the 244.
The EQ itself is a bit better on the 244, which affects sound quality in a direct way. The 244 has 2 bands of sweepable eq, and the 424mkIII has a fixed hi/low EQ and a sweepable mid EQ. That's probably like splitting hairs after a while, but I believe the greater tonal flexibility is in the 244's 2-band sweepable EQ.
F/I, with the 244's 2-band sweepable EQ, you can pretty much dial in the eq bands that are best, or most desirable. In the case of the 424mkIII, if you add too much boost in the fixed hi/low EQ bands, you may be introducing EQ across all channels, that the fixed nature of the frequencies may tend to induce more indistinct muddiness, rather than clarity.
At a certain point, assessing the value of the relative styles of EQ on the 244 vs. the 424mkIII is like splitting hairs, but I think 244 gets the edge on EQ design and worthiness. Having said that, the EQ on the 424mkIII is still a very functional and nice EQ, but maybe just not as nice as the 244's.
The 424mkIII has 2 speeds and the 244 is strictly a 2x machine. The 424mkIII has dbx defeat and the 244 has none.
The 244 has Access Snd/Rcv patch points on all channels PLUS global 4x2 Aux-snd/rcv system, so it's slightly a cut above the 424mkIII's 4x2 Aux/Eff-Send/Rcv system. That one is a bit like splitting hairs, again, but I think the 244 has the slight edge on Eff/Aux send/rcv.
The 244 has a dedicated stereo cue system, that may also be "borrowed" for use as an extra Aux-send. Contrast that with the 424mkIII, which has two Eff-sends, but switches one 4x1 Eff-send circuit, to "borrow" it for purposes of a MONO cue monitor/headphone-mix section. This is a case where opposite designs prevail on each machine. A dedicated stereo cue sytem is definitely better, though. Stereo cue and more than adequate ACCESS SND/RCV patchpoints, PLUS dedicated STEREO Aux-Send/Rcv system gives the 244 the edge in effex-interconnectability.
EQ is something that affects the sound of a recording in an immediate sense, as does the complexity of the front end mix you're laying down to tape, so the 244 fares about even with the 424mkIII, overall.
Build quality is better on the 244, by far. Further, with the 424mkIII having a power "module" it's not a truly self contained solution,... a small consideration, but still a differing factor.
You did alright to score a low use 244 that you're happy with. The sound quality of that machine can't be compromised, no matter how much a fan of the later Portastudios you are.