We are going to Zurich August 28, arrival at 11:25 a.m. and leave
Zurich September 1 at 8:00
p.m. and will stay at a hotel in Zurich. We want to see Switzerland
and France during that time. How do I plan to see major
tourist attractions in the two countries? Which is more conveinient
and comfortable: Eurail or bus?

Rail is more convenient, no traffic jams, no drunk drivers, you can
move in the train when you're tired of sitting down... The rail
service is very efficient in Switzerland, a little less in France (but
not so bad) and it enables you to arrive at the heart of cities
directly.

answer based on my own knowledge of transportation system (lived all
my youth  next to the swiss border, familiar with both systems)

If by Eurail you mean a pass sold in the USA, it may well be cheaper
to simply book point to point tickets direct with, for France,
www.sncf.com, or the Swiss equivalent. Passes often do not give good
value and RailEurope is almost always overpriced compared to buying
locally - see Question 388745 for an example.

Also note in Switzerland there are numerous private railways which are
not covered by Eurail pass.

Owain