I don't mean the full OED. Personally I have a Pocket Oxford and a Concise Oxford. Both are space constrained. The Pocket Oxford in particular has around 60,000

I don't mean the full OED. Personally I have a Pocket Oxford and a Concise Oxford. Both are space constrained. The Pocket Oxford in particular has around 60,000 words so leaving out the most common 5-10K would make a noticeable difference. Since it's the complex words that get left out in small dictionaries, as you decrease dictionary size, the size saving that you'd get from removing common words proportionally increases. But you might be right that it wouldn't make enough of a difference, since small dictionaries can also fit less words in total. It might never be enough to matter much.