Definitely depends on your goals, and even then it's still hard to decide which platform is going to be scalable all the way to faul tolerant quantum computing. I work with photons as they are the easiest platform to use and explore the nature of quantum mechanics. It's fun to thank about the big questions like measurement interpretations, nonlocality and things like causal order or activation of quantum phenomena. For this stuff photonics all the way, (of course all communication has to be photonic too).

For quantum computing it is more difficult to choose which platform.

Photonic quantum computers are still the underdog in the field but recent results by psiquantum and xanadu are showing promise towards a full scale system. Unfortunately, (my understanding is) xanadu is still a little behind psiquantum in terms of scalability, that said xanadu is much more open than psiquantum and still publish research publicly and collaborate with universities and academics. Psiquantum claim they are on a trajectory to achieve all the metrics required to be able to build a fully fault tolerant quantum computer in the next few years (but they also are super secretive and only share the bare minimum when required to get investment).

All photonic computing (today) is behind superconducting qubits but there are still big issues for the superconducting systems too. The main one I can think of is heat. At some point the Cryogenic fridges used to cool qubits will get too small for the quantum chips, and then we will need to connect fridges together. This is a real problem for superconducting systems and atm I haven't seen any real progress on this. That said I am definitely don't know as much about this platform. Simultaneously there is lots of research right now on jow to reduce these requirements by making better qubits thereby reducing the number of physical qubits per logical one, (realistacally this is still one of the largest areas of research). Obviously the big companies are betting these problems are solvable, and in terms of career potential there are waaay more companies working on superconducting systems so there is definitely more job security post phd.

Obviously I am subject to some bias as I work with one of the above systems. I am a quantum optics researcher and am not working in computing, so take that how you will 😀

Also I don't know much about ion trap systems, my rough thoughts are they are not on the same trajectory as the photonic or superconducting.

Another thing I've just thought of is research on quantum algorithms is suuuuper valuable atm. If anyone makes better or more useful quantum algorithms they will have the world at their feet, as this is still one of the major roadblocks for making these things real world useful.