Difference between One piece Toilets Vs Two piece Toilets
First thing first , let me explain what is one piece toilet and what is two piece toilet. The main functionality of both the toilet are flush out the waste from human body.

A water closet consist of three parts, they are bowl , pedestal and a tank. Pedestal of the toilet is to give the required height for the toilet. Bowl in the toilet is designed to collect the waste and flush out the waste to the drain pipe line. Tank is to store the water and provide required pressure to flush out the waste from toilet.

If the toilet and tank is fused together without any joints then the toilet is known as one piece toilet. It is also known as single piece toilet.
If the toilet and tank are separate and joined using fittings then it is known as two piece toilet. it is also called as coupled toilets.
Find ten types of toilets here.
Now let’s dive into the comparison..

When we buy anything price will be considered a major point. One piece toilets will be much higher price than the two piece toilet. Because of the Production difficulties to produce an one piece is much higher than producing a two piece toilet. so the cost of one piece toilet is double than a two piece toilet. The winner is Two piece toilet.

Design availability:
Normally both the toilets are available in similar designs. As you can see in the below two models of toilets, design of the toilet are same but you can get single piece or coupled closet, that is your choice. So design wise both are same.

Aesthetic Look:
When you compare between coupled closet and single piece toilet based on look, then definitely one piece toilet is a clear winner as the product made with out any joint or gap between tank and body.

Weight:
One piece toilets are designed to with hold the ceramic tank during firing cycle in production cycle so in design itself the products are higher in weight. Normally the weight of a single piece toilet is around 40 Kgs(88 Pounds). A two piece toilet weight is around 25Kgs (55 Pounds). so with solid mass the winner is one piece toilet when comparing weight.

Mounting Options:
As we seen before the weight of a one piece toilet is higher when comparing to a two piece toilet, because of the more weight one piece can’t be hanged in wall. So for coupled closets you can get wall mount and floor mount models, but for one piece only floor models will be available. So if you are looking for a wall hung model then you have to go for two piece toilet.

Size:
The size difference between one piece toilets and two piece toilets are not much as both are nearly same in size. But if you look at transportation option then two piece can be easier because you can get toilet and tank separately. Height of the both toilets are around 400 MM (15.7 Inch).

Functionality:
Functionality of the both toilets are not depend upon the toilet model. It depends upon flushing mechanism used  in the toilet and design of the toilet. So one piece and two piece toilet are getting equal points in this comparison.

Installation:
About installation we can look in two views,
1. One is, if you Look at installation of toilet and fittings then one piece is much easier to install compared to two piece toilet because the toilet and tank are already connected so no need of any mechanism to connect. Two piece toilet fitting is not much easier as one piece toilet because tank and toilet fitting need to be done carefully to avoid water leakage and proper flush functioning.
2. Second one is moving a one piece is much difficult when compared to two piece because of the very high weight. But moving a two piece toilet is easier because toilet and tank can be moved separately.
Maintenance:
Due to less fittings in one piece toilet the maintenance is very less. In two piece toilet problem may arise in tank and toilet joint areas.
Cleaning is comparably easy in one piece toilet because of the no joint and no gap design. but cleaning has to be taken care in two piece toilet & tank joint areas.

Other Points:
(i) Glaze color are depends upon the toilet manufacturer, normally one piece and two piece toilets are available in white and ivory color. If you are looking for double color and different colors you have to look for china made toilets.
(ii) Both the toilets you can get seat cover as soft close seat cover as well as hard close seat cover.
(iii) Both the toilets can be available in ‘P’ Trap and ‘S’ Trap.