MobileNetV2 vs Vision Transformer (ViT)

MobileNetV2 is a lightweight image classification model developed by Google Research, released in January 2018 under the Apache 2.0 license. It introduces two key architectural innovations: inverted residuals, which expand the channel dimension within each bottleneck block before applying depthwise convolution, and linear bottlenecks, which remove the non-linearity before the projection step to preserve information in low-dimensional spaces.

MobileNetV2 achieves competitive top-1 accuracy on ImageNet relative to its computational cost, making it practical for deployment on mobile devices and resource-constrained hardware. It is commonly used as a backbone for classification tasks and as a feature extractor in downstream detection and segmentation models through transfer learning. The architecture scales across a range of width and resolution multipliers, allowing developers to trade accuracy for latency based on deployment requirements.

Vision Transformer is an image classification model developed by Google Research, first published in October 2020. It applies the transformer architecture directly to sequences of image patches without convolutional layers. Each image is divided into fixed-size patches, linearly projected into embeddings, and processed by a standard transformer encoder with multi-head self-attention. A classification token prepended to the patch sequence aggregates global image information for the final prediction.

When pre-trained on large datasets such as JFT-300M and fine-tuned on ImageNet, ViT achieves competitive accuracy with state-of-the-art CNNs of the period. It performs best when pre-training data is abundant, as the lack of convolutional inductive biases makes it less data-efficient than CNN-based classifiers on smaller datasets. ViT established the foundation for transformer-based vision architectures and has influenced a broad range of subsequent models.