You can use either. Refreshing the ends with majirel and is often the most economical, however using something less alkaline such as dia richesse, or even better dialight will be better for the condition of the hair, and ultimatly last longer.
If you choose to use majirel on the ends you should make sure the mixture is suitable for the lengths and ends. For example if you added base to cover white, you would need to remix with the target shade only and add a few cm of a warmer shade (colour matching) to prevent the ends looking flat. Same goes if you used 30 vol, remix with 20 vol.
If you can get some dia light, you do get a richer, softer result. The product is acidic so very gentle and it is a very runny product so you can apply the lenths and ends very quickly.