It is honestly going to depend heavily on dive time requirements. Just getting started, you can absolutely rely on a handheld light but then you can get into the "buy once, cry once" argument and could just spend the money on a canister light with a larger battery. No issues with this approach at all.
For some people a handheld light may absolutely meet all their requirements. If and when your diving requirements grow (they usually do!) then you'll have a nice handheld primary light that you can use as backup in the future.
Handheld lights are great for open water ocean dives or even cave dives that don't exceed ~3 hours. If you consistently need runtime requirements beyond 3 hours or are doing multiple dives a day then a canister light is honestly a better option. Of course you can get multiple sets of batteries for handheld lights but it's simply really nice when you have a canister light than can burn for 6-7+ hours.
For me personally, in open water wreck diving I already have a large 20ah canister on my belt for my heated vest. I hate diving with 2 large canisters so I have switched to using a handheld light for a lot of my open water technical diving. The reality is my runtimes in the ocean rarely exceed 3 hours and when they do I am typically only using the light on the bottom portion of the dive itself. They work perfectly for me for this purpose although I do miss my old school HID beam in murky waters.
If I'm doing a ~3 hour cave dive, something like a DiveRite LX20+ or BigBlue TL4800P provides enough burntime on a medium setting. Once you start regularly exceeding 3-4 hours then in my opinion it's not a lot of battery reserve without significantly lowering the brightness of the light itself.
My wife and I normally use handheld lights for sidemount cave diving. The main reason for us was they are smaller, easier for airline travel, we don't have to deal with the cord. Also - none of our canister lights currently have the "sidemount" 90 degree gland.
Honestly I really love using a handheld light for sidemount cave diving. Unfortunately on longer cave dives we are really hitting the limits of handheld lights and will probably both end up buying smaller canister lights for travel in the future. For cave diving with backmounted doubles, 100% we always have our canisters.
Some benefits of canister light
-Longer runtime for longer dives, multiple dives, multi-days of diving without charging
-Can usually run them at higher brightest for far longer. Great for murkey water or larger passage
-Corded so you can't "lose" the light. Unfortunately I once lost a handheld on an open water dive when the line I tied a boltsnap became frayed. That was an expensive dive.
I'd personally look into the new DiveRite FX40 handheld if i were just getting started. It has a very reasonable runtime for handheld, with a nice tight beam (although personally I have not seen it in the water yet). The new DGX canister light also looks very good for the price. I think it's a rebranded OrcaTorch but with DGX support / customer service.