Which way I should go, Relay or Triac Switching?
Relay

Has low voltage drop when closed.  Other than not exceeding the max current rating, you don't worry about dissipation.

Inherently isolated.

Can switch off at any time.

Is relatively slow, ms to 10s of ms to respond either direction.

Is a mechanical system, so eventually wears out from use.  Consider each relay as capable of a finite number of switch cycles.  Good relays come with specs for this.  Note also that the current, voltage, and inductive component of the load being switched can significantly effect the number of switch cycles a relay is capable of.



Triac

Has a volt or more drop at useful currents.  The little bit of reduced voltage to the load is usually not a issue when dealing with line voltages, but the power dissipation can be.

Not isolated.  This can be a serious issue when switching line power.  Sometimes the control circuitry can float with the line voltage.  Sometimes optical isolation is used right before the triac.  That's so common, triacs with optical isolators come packaged in a single device called a solid state relay.

Turns on pretty much instantly, certainly much faster than a relay.

Turning off only happens at a current zero-crossing.  This can be both good and bad.  It is good in reducing emissions.  It is bad if you want to turn something off quickly.

As long as maximum specs are adhered to, lasts pretty much indefinitely.