大同小异 Generally the same, but slightly different
Explanation
形容事物大体相同，只有细微的差别。
To describe things that are generally the same, but have minor differences.
Origin Story
在一个古老的村庄里，住着两个名叫小明和小华的男孩。他们从小一起长大，几乎形影不离。他们都喜欢踢足球，都喜欢吃糖果，都喜欢看动画片。但他们也有一些细微的差别。小明喜欢红色，而小华喜欢蓝色；小明喜欢吃苹果，而小华喜欢吃香蕉；小明喜欢踢前锋，而小华喜欢踢后卫。尽管他们大同小异，但他们的友谊却十分深厚。他们互相帮助，互相支持，一起度过了美好的童年。
In an ancient village, there lived two boys named Xiaoming and Xiaohua. They grew up together and were almost inseparable. They both loved to play football, eat candy, and watch cartoons. But they also had some subtle differences. Xiaoming liked red, while Xiaohua liked blue; Xiaoming liked to eat apples, while Xiaohua liked to eat bananas; Xiaoming liked to play striker, while Xiaohua liked to play defender. Although they were very similar, their friendship was very strong. They helped each other, supported each other, and spent a happy childhood together.
Usage
这个成语常用来形容两个事物或两个人在主要方面相同，但在细节或次要方面略有不同。
This idiom is often used to describe two things or two people that are the same in the main aspects, but slightly different in details or minor aspects.
Examples
-
这两款手机功能大同小异，价格却相差甚远。
zhè liǎng kuǎn shǒu jī gōng néng dà tóng xiǎo yì, jià gé què xiāng chā shèn yuǎn.
These two mobile phones have similar functions, but their prices are quite different.
-
虽然两个方案大同小异，但还是有一些细节上的区别。
suī rán liǎng gè fāng àn dà tóng xiǎo yì, dàn shì hái yǒu yī xiē xì jié shàng de qū bié.
Although the two plans are similar, there are still some differences in the details.
-
他们两人性格大同小异，都是比较内向的人。
tā men liǎng rén xíng gé dà tóng xiǎo yì, dōu shì bǐ jiào nèi xiàng de rén.
They both have similar personalities, both are more introverted.
-
这两种方法大同小异，都可以用来解决问题。
zhè liǎng zhǒng fāng fǎ dà tóng xiǎo yì, dōu kě yǐ yòng lái jiě jué wèn tí.
These two methods are very similar and can be used to solve problems.
-
这两本书的内容大同小异，都是关于历史的。
zhè liǎng běn shū de nèi róng dà tóng xiǎo yì, dōu shì guān yú lì shǐ de.
The contents of these two books are very similar, both are about history.