If you want a broader experience try the NYA. As KFC said, at the NYA you will experience a more hands on form of railroading where at the LIRR youll have a more mundane work environment where everything is basically the same day in and day out. NYA could be a stepping stone for bigger and better things for you, if thats what you choose.
As a freight conductor it will be tough at first. You'll work nights on the west end of the railroad and when youre new the overtime is crappy, so forget the 20 hrs a week. When it comes time to qualify though, youll have to know everything that the lirr guys do since it's their railroad.
Lirr is a more pampered environment, especially for a conductor starting out. You will probably work shitty jobs out of Penn station or flatbush ave nights, but you'll be comfy cozy on an M7 rather than freezing your ass off in a 30 yr old engine with no weather stripping. Rarely will a freight related move come up on the LIRR like a rail train or stone train, so be prepared to work a lot of passenger jobs. If you don't like dealing with people then the lirr isnt for you (as a conductor). I remember once hearing from a wise NYA engineer "freight cars don't talk back".
On the NYA, you wouldn't start as an engineer, you will have to go up through the ranks-first starting as a brakeman. As time goes on, you'll qualify as an engineer. Difference between Lirr and NYA is that LIRR will hire engineers off the street whereas NYA will not. LIRR engineers have the same training as NYA guys but obviously work more passenger jobs and more branches.
THe amount of information (rules) that you will have to understand and apply will be a daunting task. It will probably be the hardest thing youll accomplish in youre lifetime, so be prepared to put your family and personal life on hold for a year. But if you have the passion for railroading, you'll overlook that and soldier on.
In fairness to the LIRR guys, the old timers know their stuff and came from a time where it was a hustling, bustling freight railroad. Not so much slack was given to employees back then either. Its a different story now. There are more pardons given out and they are more lenient when things go wrong. I wouldn't go and say that that the NYA crews are better railroaders than 90% of the LIRR guys, that's not fair to say. Half of the roster on the LIRR now is brand new and they never will run regular freight in their lifetime and weren't taught it the way that you guys were. Two completely different animals. Just because a guy leaves his markers on the rear end of his leading engine doesn't mean he's a space cadet. How many times have I seen that on NYA freight jobs?? C'mon now.
Point is, if you want a more hands on and interactive, challenging environment, than the NYA is the way to go. On the LIRR, you'll get paid a lot more, but you won't have much of a varied job. Of course, with 6,500 employees, the LIRR is a great place to meet new people and advance to different positions. Not to mention the great benefits and pension. Some positions, like Engineer for example, have two pensions- LIRR and BLE (brotherhood of locomotive engineers). You'll make a helluva lot more money on the LIRR, but its very hard to get hired there, especially off the street. May you consider another route is to take an entry level job on the LIRR like a cleaner or laborer and advance that way after your year's probation is up. That is what many people do. The choice is yours. Submit your resume to lirr too and see if you hear anything back. Good luck with your endeavors!