I'm going to popular for saying this but 1 advantage of MSTS if you on a limited budget then almost all MSTS items are free,and can be down loaded from UKTS,there are a few Payware routes like MEP+ cost £4.50 from UKTS,it's on a DVD but you get the Route From Kings Cross to York and I think as far as Northallerton,plenty of Locomotives stock,about 100+ activities,also included is the various routes off of the ECML one goes as far Skegness.
Another route I can recommend is NWE v3 again all items needed to run it comes with route,and you can down load it from the MSTS part of the library,( recommend you pay£3.00 for a months premium membership,as there a quite a few items to down load,the advantage of premium is no kew waiting.
Also MSTS will run in ORTS which makes it more realistic
With TS 2013-17 everything is payware,or relies on payware items,and you might get one or two items motive power and a couple of coaches and freight items.
Ex South African Railways Employee,My favorite loco is a SAR\SAS 25C Condensing Locomotive