I ask specifically about:

eXtcal
http://dev.xoops.org/modules/xfmod/project/?group_id=1092

and

Pical
http://www.peak.ne.jp/xoops/md/piCal/

My perception is that the Pical calendar development community is by far the more active in developing their module. Is this so? What do you you think?

I currently use eXtcal but am seriously considering a transition due to my perception.

hhttp://www.wjue.org/modules/
xoopsheadline/index.php?id=3#http://www.guanxicrm.com/
modules/news/article.php?storyid=29

found this to be better.

I didn't include that module because I've read that it has a fatal quotes bug that cripples its use.

well here is from the dev section..
CHANGELOG
2004-09-04 wjue
v2.2.0 include contribution of dheltzel

block listing sorting and grouping by recurrent events and non recurrent events
date format in blocks controlable by XOOPS settings
event search under XOOPS bug fixed
bug fixe : submission of recurrent event sometimes gave non recurrent event
minical block show image setting accessible from XOOPS standard admin panel
minical block show today's event setting accessible from XOOPS standard admin panel
minical block show photo sponsor link setting accessible from XOOPS standard admin panel
minical block image url link setting accessible from XOOPS standard admin panel

contribution of dheltzel : some useful features !
added a preferences page to the admin area to set most of the vars formerly set in config.inc.php
added options to minical block for source/link url's
default contact name and email to the user's profile settings
only show "add event" if user has that permission in module views

2004-06-04 wjue
v2.1.1
permission bugs fixed

2004-04-25 wjue
v2.1
group permission system implemented
minor bug fixe

2004-02-25 wjue
v 2.0FINAL
Minical block modified
7 days upcoming events block modified
30 days upcoming events block modified
bug fixe

2004-02-18 wjue
version 2.0RC
bug fixe
7 days events block added
30 days events block added
code cleaning
security fixe

2004-02-07 wjue
version 2.0 beta2
numerous bugs fixed
minical display events fixed
added repeating event exception management

2004-02-01 wjue
version 2.0 beta1
minical random image display is now much simpler
a variety of recurrent events support
several new templates

2004-02-15 wjue
version 1.2.4
minical display on feb 2004 when week starts from monday
fixed remainning potential security problems when your PHP has register_globals on AND "remote include" is also permitted.

2004-01-10 wjue
version 1.2.2
security fixes

2003-10-03 wjue
version 1.2.1
minical display bug fix

2003-10-02 wjue
version 1.2
enhanced language detection capability
Agenda-X now uses the same date format as XOOPS
Chinese language year, month day suffix fixed
updated Spanish translation

2003-09-04 wjue
version 1.1
fixed i18n.php international translation bug
other bug fixes that I forgot the list...
code cleanning

2003-07-27 wjue
version 1.0.5
add admin "list active/expired events"
minical weekday mini image alignment with block width
add Italien, French, Spanish and Portugal translation

2003-07-15 wjue
version 1.0 Final
added XOOPS site wide search
numerous bug fix
new design of Minical Block


2003-07-08 wjue
First public release v1.0 RC

Is the quotes bug fixed? I didn't read anything in your last post to say anything to the contrary.