Digi not really after merger with Celcom but Hotlink yes. But Maxis Hotlink coverage has been very bad recently. You should have no problem in big cities but rural area is simply worst. Unfortunately Celom Digi coverage is the best.

Unifi Mobile has longer validity but doesn't have so called RM30-50 for a year validity subscription. And you better check download the mobile apps and check the validity and make sure to top up to continue keeping the number. Once they detected long no topup inactivity they will decomm your number instantly the moment you hit expiry date at 12am sharp. I know because I encountered this.

Hotlink prepaid RM30 a year is to keep the number, not related to any plan. You must pay the RM30 to subscribe the 1 year validity. Install the mobile app and subscribe from there.

TuneTalk basically rides on Celcom network. They are what we called MVNO operator. Celcom rented portion of unused bandwidth to TuneTalk so technically they have good coverage as Celcom Digi now. However, the bandwidth range is limited so can be congested sometime. Overall for long validity to keep the number is ok but in terms of the data plan they are other better options. That's based on my research few months back.

Long validity yes but coverage is one thing to consider if the location is outside in rural areas. I think best to check the location coverage as well.