which HRM is best

Here are some of my thoughts for you on Polar, Suunto, and Garmin HRMs that fit your criteria:

Garmin Forerunner 50: Out of all the Garmins, only the Forerunner 50 is water resistant to 30 meters. The other Forerunners (101, 201, 205, 301, 305 and 405) are rated IPX7, which means that they're WR to 1 meter and not rated for swimming.  Pace is through the optional footpod.  I'm not certain if it tracks calories, however. I used to own the 405 and it did calories, although I wondered if it was accurate with its calorie count. Those other Garmins are GPS capable and so are each bigger than the 50 and probably too big for your tastes (from what you describe).

Suunto T3c: Their T Series offers HRM.  T3c (c is for comfort belt) is probably close to what you are looking for with the optional foot pod for pacing and cadence. The T1 and T1C would be good but you won't get pace.  The T Series also come in women versions (extra colors, different wrist straps, etc). 

Polars (various): If you liked your Polar, why not stay with them?  I think they do a very good job when it comes to HRM as it is their specialty.  The problem is, there are so many Polars to choose from its hard to know which one to buy.  They have a comparison guide on their website, polarusa.com, that might help.  You'll no doubt find several of their watches that would fit your needs to replace your old F4.  Take a look at their basic running model first, the RS200 with foot pod for pace.

Each of these brands has their own proprietary program for downloading data.  I'm familiar with Garmin, which is ok but basic but you could always load directly onto BT.com, and Polar's Protrainer 5, which is pretty good.  I've not heard good things about the Suunto program and many serious runners with Suuntos just go with a third party such as Trainingpeaks.

I don't know of any one site that compares these three brands objectively.  You kind of have to use their sites, as well as check the reviews on amazon.com, REI.com, suuntowatches.com.  Buy from REI to get their great guarantee, which protects you above and beyond what the manufacturer warranty will do.  Happy shopping.

Thank you!  that is a great overview