Is insulating basement ceiling or first-floor walls more effective

Any recommendation depends on your location - I wouldn't provide the same answer for Yuma, AZ as I might for Edmonton, AB.

When water vapor diffuses through a wall and reaches the exterior sheathing, if that sheathing temperature is below the dew point the vapor will condense. Depending on the amount of water vapor and the rate at which the wall cavity is able to dry out, this may lead to moisture problems.

Installing insulation in the wall cavity will help reduce heating costs, but won't address the problem of sheathing temperature. As a result, some builders are specifying 2" to 4" or more foil faced polyiso panels be installed outside of the sheathing to raise the temperature above the dew point. In these designs, some don't even advocate using cavity insulation. Vapor will still diffuse into the cavity, but it will not condense on the sheathing surface.

Installing foil faced polyiso on the interior of the wall, properly air sealed and with taped joints, forms an effective vapor barrier which will reduce the problem of moisture diffusing through the walls. However it may not solve all of the problems with vapor diffusion so it's quite possible to still have problems.

Additionally, while most people look to insulation as a primary solution for energy savings, often older homes would find greater benefit from air sealing. There is almost no way you can make an older house with plaster walls "too tight." In fact, the idea of houses being "too tight" is something of a myth. Your goal should be to have "managed ventilation" rather than the unmanaged ventilation common in older homes.

In my 1870's New England house as an "inside" solution I removed the plaster, installed fiberglass batt insulation in the cavities, applied 2" foil faced polyiso over the studs (for a thermal break and vapor barrier), with 1x3 furring strips and gypsum on top.

Thermal insulation (and a vapor barrier) is applied between the interior and exterior surfaces of the home. Unless you plan on leaving your basement unheated, you wouldn't place thermal insulation between the floors. And leaving it completely unheated is a bad idea since pipes can freeze.

The only reasons to place insulation between floors is for sound or to slow the spread of fire. For fire protection, the places you'd install insulation are where fire could spread up an opening like a chase for running duct work and other utility lines.

What's left is sound protection, and that is best provided by using flooring materials like carpeting above, and then separating the drywall from the joists with something like resilient channel. Insulation in the ceiling cavity will only reduce the high frequency sounds from above. The low frequency sounds, such as loud footsteps, will travel directly through the flooring, the joists, and be rebroadcast by the drywall. Think of sound like electricity, the joists as a short, and carpeting and resilient channel as tools to prevent that short.