bert-base-uncased and xlm-roberta-base are both fill-mask models. See each entry for specifics.
Google's original BERT base model in uncased form, pre-trained on BookCorpus and English Wikipedia via masked language modeling. Tokens are lowercased before processing, making it insensitive to capitalization. It remains a standard fine-tuning base for classification, NER, and extractive QA, though newer encoders outperform it on most benchmarks.
XLM-RoBERTa base from Facebook AI, pre-trained on 2.5TB of filtered CommonCrawl text across 100 languages using the RoBERTa training procedure. Enables cross-lingual transfer — models fine-tuned on labeled English data can infer on other languages without parallel annotations. The standard starting point for multilingual classification and token-level tasks.
Pick based on your compute budget and specific task requirements.