GDSM versus SDSM

Gray dragon scale mail (GDSM) and silver dragon scale mail (SDSM) are considered the two best suits of armor in the game. GDSM provides magic resistance and SDSM provides reflection, but it is not always clear which is better in any particular situation. If you intend to wish or reverse-genocide for dragon scale mail, you will need to decide which one is more appropriate.

Sometimes the armor that would be most useful immediately is not the one that you intend to include in your ascension kit. In this case, you must choose between maximizing immediate utility, and conserving wishes in the long run.

Gray dragon scale mail

 * Magic resistance protects against many monster spells, including particularly nasty ones such as destroy armor and touch of death.
 * Bear in mind that attack spells generally require the monster to be in melee range, so careful use of missile attacks and/or Elbereth can mitigate this danger to some extent.
 * Magic resistance protects you from wands of striking, which cannot be reflected.
 * Wands of striking do less damage than the elemental wands, and will not damage your equipment.
 * Magic resistance provides protection from teleport and level-teleport traps, which can place unwary characters in dangerous situations.
 * Magic resistance provides full protection from polymorph traps, and allows you to safely displace your pets onto them.
 * SDSM provides partial protection against polytraps: you will turn into a silver dragon, trashing your shirt and cloak but keeping your armor. This will not protect against subsequent polymorphs while in silver dragon form, or against lycanthropy.
 * Reflection is usually easier to obtain without wishing than magic resistance, particularly because of the possible amulet of reflection in Sokoban and the possible shield of reflection on Medusa's Island. Spending a wish or genocide scroll on GDSM makes it easier to obtain both properties.
 * Obtaining magic resistance from your suit frees up your cloak slot. This allows you to wear something more useful, such as a robe or oilskin cloak.
 * On the other hand, you will need to employ either an amulet or shield for reflection.

Silver dragon scale mail

 * Reflection protects you and your equipment from wands and breath attacks of fire, cold, and lightning.
 * You can protect scrolls and potions against fire and cold by placing them in a container. Rings and wands kept at the ready will still be vulnerable to lightning.
 * Accidentally attacking a floating eye will not paralyze you.
 * Careful play will usually prevent floating eye accidents.
 * While both suits protect against a wand of death, reflection gives a chance of killing the zapper on a rebound, preventing him from wasting valuable charges.
 * Obtaining reflection from your suit frees up your amulet and off-hand slots. This allows you to wear another amulet (such as life saving), and potentially allows two weapon combat and combat spellcasting.
 * On the other hand, you will need to employ either a cloak or a (wished-for) quest artifact for magic resistance.