I recommend WinSPWW2.
SPWW2 is better for PBEM and against AI.
WinSPWW2 is still supported. See here:
http://forum.shrapnelgames.com/forumdisplay.php?f=139
Here's some of the differences:
Windows compatible
SPWaW: Not Windows compatible
SPWW2: Full Windows compatibility
Screen size
SPWaW: 800x600 (full screen only)
SPWW2: Up to 1600x1200 or 1920x1080 (paid version)
SPWW2: Windowed or Full Screen
Map Size
SPWaW: 240x100 hexes (12x5 KM: 60sqKM)
SPWW2: 200x160 hexes (10x8 KM: 80sqKM)
Hill Levels
SPWaW: 3 hill levels
SPWW2: 15 hill levels
Zoom Levels (map magnification)
SPWaW: 5
SPWW2: 6
Maximum Units
That a player can deploy in a battle.
SPWAW: 400 units
SPWW2: 500 units
Maximum Formations
That a player can deploy in a battle.
SPWAW: 100 formations
SPWW2: 200 formations
Maximum Game Turns
SPWAW: 60
SPWW2: 90
Infantry Uniform Colours
SPWaW has 4 infantry uniform colours
SPWW2 has 5 infantry uniform colours (6 if you include snow camo mods)
Nations Available (OOB Breadth)
SPWaW: 27 OOB
SPWW2: 36 OOB
OOB Depth (unit choices)
SPWaW: German OOB: 260 units
SPWW2: German OOB: 980 units
Credit to Alby, Panzer Leo and others who have done some excellent OOB mods for SPWaW
Unit Classes
SPWaW: 113
SPWW2: 255
Sounds
SPWaW: 600
SPWW2: 150
This is one area where SPWaW is superior to SPWW2.
The SPWaW sound engine has better quality and a greater variety of sounds.
There is a SPWW2 sound mod which improves the quality of the SPWW2 sounds; and many of these sounds are better quality than the SPWaW sounds, but the mod is still only 150 sounds.
Artillery
SPWaW: Arty falls at end of own turn
SPWW2: Arty falls after opponent has moved
The artillery routine in SPWW2 is far less gamey.
SPWaW unrealistically allows you to adjust artillery onto fast moving vehicles.
Armour
SPWaW: mm
SPWW2: cm
SPWaW measures armour in mm instead of the cm used by SPWW2.
This really makes no difference to combat resolution results.
SPWaW models low penetration weapons (like Anti-Tank rifles) against light armour (5mm to 10mm) with more specificity.
Opportunity Fire
SPWW2: Unloading units attract ‘opportunity fire’
SPWW2: Opportunity fire filter (paid version)
SPWaW: Humans choose when/if to op-fire against AI
The SPWW2 ‘Opportunity fire filter' allows ATk guns (eg.) to choose target and range.
Although SPWaW players can choose when/if to op-fire against the AI, but some point out this gives human players an unfair advantage over the AI.
Misc Unique Features
SPWW2: PBEM Campaigns for 2 human players (paid version)
SPWW2: Shoot through smoke/ non-line of sight area fire
SPWW2: Paratroops draw ground fire while descending
SPWW2: Motorcycle troops can dismount and fight
SPWW2: Reversing Tanks
SPWW2: Infantry can attempt to take cover at end of move
SPWW2: Move points to load/unload infantry from vehicles, ends gamey relay tactics
SPWW2: Choose rally/retreat direction
SPWW2: Blast circle option
SPWW2: Timed objectives
SPWW2: Guns/vehicles parachute separately from crews
SPWW2: Company/formation identity numbers (paid version)
SPWW2: Snow camo for vehicles
SPWW2: Snowmobile movement class
SPWaW: Command Control (limits orders each turn)
SPWaW: Suspension damage
SPWaW: Weather (may restrict visibility and movement)
SPWaW: Time of Day (may restrict visibility)
SPWaW: * spidy sense (SPWaW weakness, fixed in SPWaW Enhanced)
SPWaW: Teleporting infiltrators (SPWaW weakness)
SPWaW: Numeric indication of number of men over squad/section
SPWaW: Reduced (not full strength) squads/sections option
Misc Superiority
SPWW2: Location specific map generation (SPWW2 is better)
SPWW2: AI sophistication (SPWW2 is better)
SPWW2: Ammo re-supply realism (SPWW2 is better)
SPWW2: PBEM security (SPWW2 has additional security level)