Your layout's motive power

[aloco]

If I'm running road engines I usually use two. Mostly four axle units.

Yard engines, mostly one by itself or sometimes two. 

Almost all locos are first generation diesels (built in the 1940s and 1950s) and most are in modern paint schemes (I model the year 1974 in HO scale).  

Typical train length is about four or five cars (my layout is quite small).

 

[BerkshireSteam]

Ok I read that and I don't think I sounded very clear. As an example a model rr could use a 3 unit lash up of SD40's for say a 60 TOFC manifest or a 100 car unit coal train while the prototype may use the same lash up for a TOFC consist but use 6 unit lash up for a coal train. So do you go with what works, a 3 unit lash up, or what would be more prototypical, a 6 unit lash up, even if it's overkill?

[BerkshireSteam]

How do you choose power for your layout? 6 axle or 4? 2 units or 6? I asked a similar question in the trains forum and thought I would ask about the modelers point of view. The inquire came to light because while our model trains aren't as diverse in power from model to model, a Kato SD40 will pull about the same as a Kato SD70, as it is with the prototypes, an SD40 has 3000hp with XXXX TE and an SD70 has 4000hp and XXXX TE, they still basically balance out. A video on the Cajon Pass showed a spline car consist of about 60 cars powered by a GP60M/B/M/B lash up would be run as the same on a model layout. To a point it does balance out, at least I think.