Tempest sounds great, and has a unique character.
The UI layout is fantastic, and it has way more to offer in the realm of synthesis.
Each of the “Modes” are really fun in how they work.
The Tempest kind of begs to be played as a standalone device, or at least with one other mono synth or something.
You can sequence up to one external device from the Tempest.
CC automation, and midi implementation on the Tempest are extremely limited.
I find that to get the Tempest to sound really expressive, you need to be hands on most of the time.
I found the biggest draw backs to the Tempest being how limited it is in programming.
There are no “banks” really, so you can run out of patterns quickly.
The idea is that you can mute pads, to create multiple patterns within 1 pattern, however there is an 8 event limit (only 8 things can happen at once, even when pads are muted). This odd limitation makes the solution for limited patterns feel even more limited.
If you want to save or load anything on the Tempest, you have to stop the playback.
I think the samples in the Tempest seem like an after thought. There’s a bunch of random shitty samples that makes me think why even bother.
The Compressor and Distortion kind of feel like a one trick stomp box. They are ON, or OFF, not much else other than more ON.
Touch sliders on the Tempest feel kind of reckless. There’s nothing "smooth"about using them.
If I remember correctly, assigning the High Pass filter to a slider doesn’t work very well at all, you go from zero to lots of high pass worth not much in between. When assigning stuff to sliders, you have to treat them as something that less about precision, and more about mangling.
Tempest has no FX.
The Tempest is an amazing machine that sounds fantastic and is designed to jam on, but it demands your attention to shine.
If you’re into the idea of having minimal analog drums, along with lush synthy sounds and an quirky/cool round robin voice thing, that’s super fun to tweak knobs to oblivion, the Tempest is where it’s at fer sure.
As a drum machine and possible the heart of a system of multiple synths, the RYTM crushes the Tempest.
From a programming songs standpoint, Elektron leaves Tempest in the dust.
Samples sound like magic in the RYTM.
The analog machines sound fantastic, massive low end.
Not a lot of sound shaping synthesis for each machine. The RYTM seems designed to be very focused.
A kick drum will be a kick drum, not really a “lush synthy pad”
The combination of samples and analog machines make a wide pallet of percussive possibilities.
You can make HUGE bass lines and leads using single cycle waves in the RYTM.
The compression, overdrive, and effects are really nice and have just what you need for editing options.
For finger drumming, the pads on the RYTM are stupid small, and trying to tap out a meaningful velocity seems impossible. The pads work great for the Perf Mode, Scene Mode, Mute mode. I’m completely satisfied with their expressiveness in Perf Mode.
P-locks, and conditional trigs take the RYTM to a whole new level on what you can achieve with 1 pattern.
One LFO per track seems pretty limited.
Sample management is kinda wacky and definitely takes time to get use to, and then once you understand it, you’ll ask “WHY!” a lot.
The playable “re-trig” function on the RYTM seems very unfinished or not thought through.
The are both great machines, but really different from each other.
To me the Tempest and A4 is a better comparison, or at least a closer one.
As someone stated earlier.
Do you a want a drum machine? -> Get Rytm
Do you want a rhythm synth? -> Get Tempest
Nah, both sound great no doubt, and either one would be a killer centerpiece in any home studio 
