The two 'best' are usually Fein or Bosch, the newest versions with the Starlock system.
Other brands usually work, some better and some not so better.
Lowest price? HF single speed model. It's
LOUD, vibrates like crazy, need to use (and not lose) a hex key and two (or three) hands to change blades, not super powerful. On 'sale' (sale or coupon), it's about $10-$20. It works (somewhat). Did I mention that it is LOUD?
But the newest Fein and Bosch Starlock machines have tool-less blade changes (other machines have tool-less blade changes, so that is not the only 'difference' between brands/models), simple and quick and you don't even have to touch the 'old' blade!
And the $#^@@ 'new' (proprietary to Fein and Bosch so far) OMT blade interface works nicely. And there really is no price difference between Fein/Bosch Starlock blades and the previous version (the semi-universal OMT blade interface) Fein/Bosch blades.
And YES, get 'good' blades. **** blades are ****. And 'decent' name-brand blades seem to run about $8-$10 per blade for 'regular' blades (not diamond or carbide grit tile/grout blades). And they do make bi-metal and carbide-tipped OMT Starlock blades
But the biggest benefit (and what makes the newest Fein and Bosch OMTs with the Starlock blades the 'best' IMHO) is how 'smooth' they are. Powerful (for an OMT, they are not a 15 amp circular saw or 11 amp angle grinder, after all) and both companies seem to have really-really worked on vibration reduction (among other things).
Best high-end bang-for-the-buck IMHO? The new Bosch GOP40-30C OMT with StarlockPlus. Variable speed, 4 amp motor, LED light in the nose (not the greatest, but usually 'adequate' in dark/darker areas, nowhere near enough light to work in a shadowed area in bright sunlight though), hard case and a decent assortment of blades. Decently long(ish) power cord (no having to instantly reach for an extension cord). Pretty darn smooth and not overly loud (unlike the HF single speed version!). And the tool-less blade change? Really slick and handy and quick, no touching the (probably HOT) blade you were just using, just flip the blade change lever and the old blade pops right off, let go of the lever and push the new blade onto the nosepiece until it clicks into place, done. Slick. And the motor is soft-start, so it ramps-up in speed instead of instantly going to full speed. Nice for control when starting the tool.
The recent Starlock Feins (250W MultiTalent and 350W MultiMaster) are also very nice, with very good vibration reduction. But a bit more expensive then the (already higher-end) Bosch. And no light in the nose. If that matters to you.

YMMV.
Check CPO Tools. They usually have competitive pricing. And despite the name, they also carry/sell new tools as well, not just refurbs.