How heavy is your friend? Cura 4s are monster brakes. The Cura 2 could be more up their alley if they are light. Easy to bleed with mineral oil with dual syringes. Have a long lever throw in the 4 pots, but is better in the 2 pots.
TRP Quadiems have the most solid build quality of any brake I've seen recently. Absolute tanks. Modulation is excellent and the power is good if you have Uberbike Racematrix pads. I've seen these and the Slate T4s for sale on Ali.
If you're friend is made of money, the XTR race lever has good modulation as it doesn't have the cam system. Pair with 4 pot calipers for a really bling brake.
If they don't have a lot of money the MT410 with sintered pads is surprisingly good. Again no cam system. You can pair the lever with a deore 4 pot caliper for the Min/Max champion. Best to get the individual parts from Ali.
Personally don't like Magura because of the fragile plastic lever bodies.
Haven't tried the Hayes Dominion, but all the reviews and feedback is good.
SRAM have just released the DB8 which uses mineral oil and runs code pads.
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