Here is what I spotted to be the major changes between 5th and 6th editions. Let me know if I missed anything, or you disagree with something I interpret. The major changes are in magic, with everything else being tidied or made more consistent. There are also rules for Siege and Mordhiem-type games.
Rules:
Characteristics -
 | The second re-roll counts, you may never re-roll a single die more than once. |
| Roll equal or less to pass a stat test, a natural 6 for a stat test always fails. |
| Zero stats for WS means you auto hit target, for S T or W means model is dead. |
Units -
| Contradiction here: page 23 says: Standard in the middle, with regiment leader and musician to either side. Page 49 says: If there is not enough space within the (front) ranks, models can be arranged into the rear ranks as the player wishes. Page 108 says: Standard bearer and musician must be placed in the front rank. |
| Musicians add +1 Ld when trying to rally, and win drawn combats if the other side doesn't have one. |
| Unit Strength; units have a mass value (eg. Infantry = 1, cavalry = 2 per figure), a side with the higher unit strength gets +1 combat resolution. |
| Models in the last rank are placed in the middle, if flank charged, they "shuffle" to engage the enemy (if appropriate). |
Movement -
| Barding (only) reduces movement by -1" move. |
| Turning 90 or 180 degrees reduces movement by 1/4. |
| You can Reform (any direction and/or formation) but not move at all, no test needed. |
| Chargers can redirect charge if target flees. |
| Lose rank bonus when charged by a unit with unit strength of 5 or more. |
| Fleeing troops initially move directly away from its enemy, closest part of unit is 2d6/3d6 away. Subsequent rounds it flees off battlefield ASAP (usually to closest table edge). In both cases it ignores terrain penalties. |
| Pursuit is similar, equal or greater roll destroys fleeing unit. Always move full roll, ignore terrain penalties. |
Shooting -
| Declare and guess all units which must have range guessed (cannons etc). Then in any order you wish, resolve a unit's shooting. Select next unit till finished. |
Armour Saves -
| 1 always fails. Only one ward save, per wound, ever. |
Close Combat -
| For Combat Resolution you only get +1 total from having any number of standards in combat, including battle standard. |
| Overkill from challenges now max of +5. +1 from bigger unit strength. |
| When lapping round, you get flank and/or rear bonus as long as the whole unit has Unit Strength of 5 or more. |
| Overrun Rule: if you kill all enemy in first turn of combat (not forced to break), then you may move directly forwards 2d6" or 3d6" depending on M. Hitting new enemy counts as charge next turn. |
Psychology -
| Panic and Fear tests now based on Unit Strength size. |
| Frenzy troops only get +1A. |
| Hatred only get to re-roll misses in first turn of combat. |
| Stubborn troops get to take Break tests on their unmodified Ld, if character is not Stubborn then Ld test is modified (may use best number). |
Advanced Rules:
Weapons -
| Using (non-magic) Handweapon and shield only to get additional +1 save in close combat. |
| Two-handed weapons only strike last when using initiative to determine order. |
Characters -
| when by themselves, on foot, and have less than 5 wounds (starting) may ignore terrain penalties (can't cross impassable still) and may see and charge 360 degrees. |
| Individual characters may always march move (ignore enemy within 8" rule). |
| If character is in unit which is fighting, and he is not in contact, may move next turn within unit to contact enemy. |
| Characters not in first rank may not fight, use magic or items, or use their Ld for tests. |
Flyers -
| No flying high. |
| Flying movement is a glide of 20". |
| Flying units always operate as skirmishers. |
Special Rules:
Scouts -
| must be set 10" away from enemy and behind/in terrain, or deploy normally. |
Poison -
| a hit with a natural 6 from a poisoned weapon wounds automatically. Armour saves as normal. |
Skirmishers -
| Never move in regular units. |
| Up to 1" apart. |
| Have 360 degree line of sight (shooting and charging). |
| No penalties for terrain and always march (but cannot shoot if move more than normal M). |
| Block line of sight, but can shoot through each other. |
| In close combat they form up like a regular unit, try to get as many into base contact as possible. |
| Do not get rank bonus, and do not cancel enemies if flank/rear charge. |
Fast Cavalry -
| Free reform in movement. |
| When shooting (not stand and shoot) can fire 360 degrees. |
| Can shoot and march (still get -1 for move and shoot). |
| Fleeing fast cav which flee as a charge reaction and who next turn pass their rally test can reform and move that turn. |
Warmachines -
| Can turn any amount and shoot. |
| Cannot march, charge, or move and fire. |
Chariots -
| Act like one big monster now, no more removing horses or crew. Most other stuff the same. |
Magic:
Choosing spells - randomised, can default one spell to the first one in the list.
Casting spells - spells now have a cast value which must be equalled or bettered. Minimum of 3. You can roll a maximum of dice of (wizard level)+1 dice.
Power dice - each players turn they get power dice equal to 2+(the total of all wizard levels), ie. one level 2 plus one level 3 equals 7 power dice. These are used up (for that turn) when casting.
Dispel dice - each opponent gets dispel equal to 2+(one for 1st/2nd level wizards, two for 3rd/4th level wizards), ie. one level 2 plus one level 3 equals 5 dispel dice. These are used up (for that turn) when dispelling.
Miscasts and Irresistible force - a double 1 is a miscast roll on table. a double 6 cannot be dispelled at all. a Miscast takes precedence over an Irresistible force (say if 4 dice are rolled). You may not re-roll a die from a miscast, it happens straight away.
Dispelling - the opponent may throw up to as many dice as they have, they must equal or beat the total rolled by the casting player.
Spells in play- after the casting player finishes, her opponent may
try to dispel spells in play, she must only equal or exceed the original base casting
value (including Irresistible spells). Then the casting player may dispel spells in play
with left over power dice.
