Deep learning models for brain tumor MRI classification are usually compared by accuracy alone, on public datasets whose independence is rarely checked. We benchmarked six architectures: two convolutional networks (EfficientNetV2-M and ConvNeXt-V2-Tiny), two vision transformers (Swin-V2-S and ViT-L/16), and two foundation models (DINOv2-L and MedSigLIP-448), for four-class classification of 7,216 public MRI images. We assessed accuracy, calibration, explainability, ensembles, and decision curves, with every fitted quantity estimated on validation data only. Pixel-verified duplicate screening showed that 36% of the test images had a near-duplicate in the training data. Test accuracy ranged from 94.5% to 95.6%, with no pairwise difference after Holm correction, and fell to 90.3% to 91.7% on the 773 test images free of duplicates and shared patients. Ensembles did not outperform the best single model. Attribution maps passed a model-randomization test but localized expert-annotated tumors poorly. On 1,675 external BDNeuro-MRI images that did not duplicate the training data, accuracy ranged from 77.6% (MedSigLIP-448) to 95.0% (ViT-L/16), and 12 of 15 pairwise differences were significant. Internal accuracy on this public collection therefore did not distinguish the architectures, whereas the duplicate-filtered external test did.

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