How it sounds isn’t a spec, but is always a major consideration IMO. It’s always best if you can try it in your system. What speakers are you going to be driving?
The power supply and current flow are significant factors in the amps ability to drive more difficult loads, so compare the 8 and 4 ohm power ratings....a true doubling of power into 4 ohms relative to 8 ohms is a good indicator.
The quality and features of the phono stage can also be a big consideration when comparing one unit to another. Options for MC and MM can be useful, as is the ability to select different cart loads.
Is a remote something you’re interested in?