Very good driver, especially for the price hard to find a better one. Used them long ago (2009 ?) in a very big transmission line with Monacor MSH116 midrange crossed over to at ~300Hz (and Seas 0,75" fabric tweeter with XO=3kHz), and had nothing to complain.
You would do nothing wrong with the SLS, it will give you very decent performance.
RS270 is nice too, as I don't like the higher mechanical losses / low Qms as I'm undecided if it comes from the aluminium voice coil eddy current losses (just loss of efficiency) or the mechanical suspension (which acts non-linear and promotes distortion) and I don't like the phaseplug design as it provides a leakage whith the risk of air flow noise at high output levels (but cools the voice coil).
My favorite price/performance 10" driver - especially for use as a "real 3-way woofer" with higher crossover up to 500 Hz - is the Scan Speak Discovery 26W4534G00 (4 Ohm) or 26W8534G00 (8 Ohm) in closed box alignment.
Found a test report by german hifi magazine:
https://www.boomaudio.de/media/pdf/2f/f3/6e/Testbericht.pdf
(you can mark the text and give it to a translator, e.g.
https://www.deepl.com/translator)
I use two of the 8 Ohm type per side in parallel, driven by one channel of a Hypex FA123 (125W), which is by calculation excacly enough to drive them to datasheet mechanical Xlim by low-bass frequencies. I put them in ~65l CB with resulting Qtc = 0,85, applied linkwitz equalization to 30Hz / Q=0,71 and use them up to 300Hz LR4.
Bass and low-mids perform outstanding crystal clear up to Pmax, you can see that the woofers deflect to Xlim, but without the funny bouncing you observe from cheap car hifi soup bowls; they are just "visually blurring", with very, very few DC offset. A guy in a german forum, who developed the current speaker line for T+A mentioned a few times that he tested and very likes this driver too. Performance at very low levels is also excellent thanks to the very few mechanical losses.
In my opinion you can't get better with a 10" if you want undistorted sound and clarity, only a few dB louder when you spend multiple the money e.g. for a Scan Speak Revelator 28Wxxx which has relevant higher linear excursion/power capabilities with also very low distortion.
Sensitivity is above average, especially for the 4 Ohm type (much higher than typically subwoofer / long-stroke drivers).
This is my beloved system (which I decided will keep as reference forever because it sound so neutral and clean - no, no, this means not that I will not build more speakers, LOL) where I use them:
If you want a really very high sensitive woofer with "in your face" low-mid punch for small cab < 30l BR alignment I would go for a Faital Pro 10PR320 or Sica 10S3PL, but they will completely lack of low-bass by physics (never used them, but by data and assumed construction details they would be my choice for that application).
A good compromise of sensitivity vs. low bass capability and much higher electrical load capability than the Scan Speak may be the Sica 10SR2,5CP, which has very good reputation in Germany - but never heard or used them myself... Faital Pro 10RS350 which his praised by Troels Gravesen is in the same ballpark, but much uglier and the Sica simulates very few better.
Maybe you give us a few more information about the forseen midrange and tweeter, Xover frequency and desired application?
Best regards
Peter