The KTM 200 Duke is a very good entry-level performance bike. Downsides are - uncomfortable for pillion, small fuel tank requires frequent refuelling and isn't suitable for long hours.
The RE Classic 350 is comfortable and with decent fuel economy. But doesn't have the performance of the KTM. If it's performance you seek, then it's the KTM, if it's Royal Enfield you like, then you will go for it anyway, isn't it?