Thanks to all who have offered very helpful responses, I now have a
much better idea of what tire I need for my city driving -- and the
advantages are towards wider tires, so my next tire will not be any
skinnier than the 700 x 35 I already have. I am even thinking I might
prefer a 700 x 40. I definitely value comfort and safety over speed
(although I do a lot of stop and starts as well, because of traffic
lights at every block). I guess no one can tell me if a 700 x 40 would
be more suited to my needs as I've outlined, so I'm gong to try to get
a mountain bike to ride.

NOW FOR THE TIRE! I will accept minimal siping if I can't locally find
a "full slick" in the 700 x 35/40 size I need. The Michelin Transworld
City I mentioned
(http://cycleus.webmichelin.com/tires/transworldcity.htm) seems to
have some pretty -deep- siping though (the only flat part is a narrow
strip of tread in the center). So I'm not sure if its the best choice
for safety's sake on pavement. Any better recommendations for COMMONLY
AVAILABLE tires, around the same price as the Michelin, that may be
"more slick" and thus provide better road contact on the pavement? (I
don't know if I can get the IRC or Avocet brands locally; but I know
for sure I can get Continental, Hutchinson, Panaracer, Michelin,
Vittoria, etc).