Upsides and downsides to riding and chasing.
I have been on some trips where I have chased, and some riding only. There are pros and cons to each. On the Craft trips of 1992, I chased the first weekend, and rode the second weekend, plus we did the Friday 3-engine trip.
As John West said, if you are going on a charter organized by a decent photographer he plans for the best locations, light, and so forth. One might get decent shots Chama-Cumbres from the highway, but the organizer might stop at some remote spot like Hamilton's point or elsewhere. The upside of riding is you get shots the chasers cannot get, and the engine/s can perform for those runbys...ie make smoke and sound great!! On the C&TS and D&S you can access remote areas of the railroad with the train, and thus riding is imperative to getting good shots in those areas. For example you can hike into Cascade Creek Trestle for an eastbound shot, and the train will trundle downgrade across the trestle. On the flip side if you are doing a formal photo runby there, the action will be better from the engine, etc.
In 2007 we did a Pere Marquette 1225(2-8-4) charter in Michigan. We never rode the train once. All chased in cars to specified locations, and group runbys were made. This was a freight with caboose, which looked like a pure freight without coaches, etc. The downside was we only went 10 miles from town on two lines and never felt like we were actually going somewhere.
The upside of riding a charter if you do not know the railroad is that everything is handed to you on a silver platter...."Spoon-fed Steam" as one of my friendly competitors would say. Thus you will likely get pretty good spots, albeit the same as everyone else. Chasing gives you more regular running scenes than the stock runby, but may not have the engine working as hard or as much smoke.
If you like being in a big crowded photo line, then riding is for you.
If you like being more away from everyone, then chasing is better.
If you are not doing charters, then I suggest riding the lines for fun, and to get a few onboard shots(regular trains), then chase a few trains for a good mix.
One downside to charters on the C&TS is that it takes so long to cover a lot of miles since the railroad is 64 miles. That limits runby time quite a bit!!
Greg Scholl
PS Its all good!!!