Sumazinti set will apply a -15% magic debuff on 5 enemies for 15 seconds.
Tiksline set will apply a debuff on only 3 enemies, increase damage to 1.5x and apply a bonus hit based on the damage you dealt in the 5 sec duration of the debuff. It also deals the bonus damage as only a single hit and will cap at 777,777 damage (will be 999,999 in future patch). Unsure if it affects summon damage or whether party members also benefit.
Honestly, Tiksline set is very underwhelming and both Sumazinti and kraujas are better in my opinion. Sumazinti’s effect is way longer and is good on enemies with high m.def (endgame content) and will provide you with a permanent boost to magic damage. It is also worth noting that since it is a debuff reducing magic damage, it is probably strong for parties with many magic DPSers as well as magic-damage summons.
Kraujas is also strong, although you will not get the boost to m.dmg, SPR, or INT. The full buff is +100% damage for 20 second duration, but you receive more damage.
If you have a build that is reliant on bursting, Kraujas or Tiksline will be better, but Kraujas is pretty much a better version of Tiksline (at least for most builds).
If you do not like having burst that relies on 100 second cooldown, then it will be better to use Sumazinti for the +600 m.atk.