Holy Cow...this is so familiar that I wouldn't be surprised if you told me that you work in the Peoria area.
PLC definitely!!!
First, let me say that I am not a fan of PC control.
I have used GE Cimplicity PC based control on a Engine / Generator / Switchgear / Load Shedding project and it had not had any problems. It was primarily for data acquisition and remote control. I did have several Fanuc 9030's in there also, along with a slug of GE MultiLin relays/controllers. The 9030's would start the standby generator, control the switchgear, and load shed through the MultiLins by themselves in the PC('s) were down. The GE people said to be careful on computer selection. They used Dell for all factory projects at the time, and also recommended Micron. The factory boys said to avoid HP and Compaq, that the GE software would crash regularly. This was in 98, so some things may have changed.
I had Steeplechase PC controller software forced on me once. Machine Builder could never get it to run smoothly, and customer decided not to use a million dollar machine. Before it was built, I mentioned for $3,000 that a complete GE 9030 could be installed, which was considerably less than the PC and software. Eventually, a new Plant Manager came in, the two robots were set up to run independently, and three micro PLC's ran the rest of the machine. Perhaps the problem was the PC's being used. This is one experience with Steeplechase, but for the expense involved, and other stuff listed on previous posts, I recommend PLC way over PC.
The Diesel Engine Generator control industry has always had a love for ice cube relays. A mechanic with NO electrical background can troubleshot them easily, and make repairs easily. Back in 72, several of us employees designed prototypes of solid state engine starting panels for the "Peoria Switchgear Leader" at that time to evaluate. It didn't go anywhere then. A couple of years later, two of our group were making pc board base autostart panels, but the times were just incorporated onto the board, and the ice cubes plugged onto it also, as opposed to seperate sockets. By the mid-eighties several solid state controls were out, but one fact remains, they will still have relays at least to control the fual valves, rack solenoids and starter motor contactors.
PLC will be best for your application. In event of a power failure, the PLC can reset and start the engine quickly. (Though not as quick as the standard 7 relays, four lights, and two timers in the oldstyle cranking panel) With load sharing, peak shaving, parallelling, etc you can't trust that the a PC won't belch at the wrong momment, and put everyone in the dark, and leave them there. PLC's will be more forgiving the the electrical noise and otherwise harsh environment where a genset is located. You should see the electrical spikes on an oscilloscope when three CAT 3600 series decide to start.
Locomotives run with embedded controllers, basically, just a type of PLC running a 6000 hp genset with 6 1000hp motors on steel wheels works fairly well.
Should you need to look for a job in a year or two, PLC's will be a little easier to find something with. If at all possible, have your employer get you some Allen Bradley training, you can use it almost anywhere. I wouldn't be surprised if your company is using a lot of GE Fanuc (My Favorite). GE is nowhere as popular as A-B, but once you are familiar with it, you should find that it has more capabilities and easier to program.
I started at REDCO in Peoria in 72, I would be interested to hear where you are at (though I have a good guess).
Best Regards.....casey