I personally think the 303 is better than the 555 for resampling ext-duties.
I made much more music on the 303 than 555 and ended up giving away the 555. The looper buffer was way too short for me. It’ll be good if you generally keep your loops short, not so much if you play longer phrases.

But the 555 lets you sample loops up to 15 seconds, which according to Roland themselves states that you'll get four whole measures all the way down to 64 BPM, and bruh, I have no intention what-so-ever of going down to 64 BPM!

And you're missing a whole bunch of abilities using the 303 over the 555, because it's not just about having the ability to monitor and record the external input while a pattern is playing, it's about how that setup can be configured and also how the sound-on-sound function can be used in conjunction with it, these things are not mutually exclusive on the 555, they work in tandem to create different workflows.

You ain't 'sound-on-sounding' any loops on the 303, you simply cannot do that without resampling manually, cause like you said, you have to build-up by resampling and do it that way. You also cannot exclude monitored audio input from the resample while still recording the internal sounds (or vice versa), nor can you generate auto-length looping samples to copy over to the pads without having to edit them by ear and guess work.

There is no question which is the better system. The only benefit the 303 has over the 555 is the length, but since 15 seconds can get you down to as slow as 64 BPM for four whole measures, it is completely irrelevant (certainly for the way I intend to use it anyway).

You also need to remember that once those loops have been copied over to the sample pads then the time restriction is gone. You can sequence-trigger, retrigger, hold and loop those samples as long as you like while still resampling them - building complete songs by doing so!

So I'd much rather have the facilities of the 555 any day, lol, there is no comparison! I do think a 303 would make an awesome partner for a 555 though (and so would a 202 for the pitch).

Sure. Whatever. Sounds like you have it all figured out in your head.
But you’re wrong about the 303.
It’s unfortunate the prices blew up.
I got mine for 75 bucks and thought I got ripped off at the time.

I've made whole tapes with just this method on the 303. superfun, almost too easy if you have bpm's synced up. Also can be frustrating if timing is slightly off and you need to resample the external source again

sp303 is probably best when resampling from an external source, though it's polyphony greatly hinders how many stereo layers you can add at once. By far the biggest advantage for the 303 is that you can turn the external source on and off while resampling! here is an example of this https://soundcloud.com/calvinhobbes/eri ... -kisses-ya
drum loop, resampled an EWF song from external source, toggled the external source to the beat of the drums

here's a similar example but no toggling. drum loop resampled with a filtered EWF song playing from external source. then resampled again with a les mcann song playing from external source. https://badvicecollective.bandcamp.com/track/airborn