Which AC is better out both brands if comparing 1.5 Ton AC with 3 star ratings?

Cooling wise both are same. Samsung offers unique windfree technology AC where instead of vent in indoor unit there are thousand pores for cool air to breeze out. Though considering Indian dust conditions we have our doubts on how these pores wont get blocked in long term. Samsung has better features however it all depends on model you are buying.

SAMSUNG 1.5 TON 3-STAR ACVOLTAS 1.5 TON 3-STAR AC
Samsung 1.5 Ton 3 Star Wind-Free Technology Inverter Split AC (Copper, Convertible 5-in-1 Cooling Mode, Anti-bacterial Filter, 2023 Model AR18CYLAMWK White)Voltas 1.5 Ton 3 Star, Inverter Split AC(Copper, 5-in-1 Adjustable Mode, Anti-dust Filter, 2023 Model, 183V Vertis Emerald, White)
Warranty : 1 Year comprehensive + 5years pcb + 10 Years Warranty on Compressor1 Year Comprehensive Warranty on the Product and 10 Years on Compressor, PCB warranty vary from model to model
Copper with Durafin coatingAnti-Corrosive Coating
WindFree Cooling with 23,000 microholes1.0 filter with aqi meter
4 Way SwingDual Temp Display
5in1 convertible4 in1 convertible

Well service wise we would say both Voltas AC and samsung Ac are same as both are well known to Indian market.

Voltas AC also offers 5 year extended warranty on its AC for extra payment where one would get 2 yearly free service from Voltas and any repair required for AC in that 5 year time would be done free of cost by Voltas that includes Gas refill if required.