According to a vowel question in Linguistic SE, English can be considered to have vowels [i ɪ e ɛ æ ɑ ɔ o ʊ u ʌ] which can be reduced to [i e æ ɑ o u ʌ] (plus an orthogonal length or diphthongization).
I use https://tophonetics.com/ for IPA phonetic transcription, which gives for "still steel" RP transcription /stɪl stiːl/, American /stɪl stil/, where I hear /i/ in American /stil/ as longer version of /ɪ/, as used in RP.
So is there a important difference? Are there minimal pairs? Does the difference depend on a dialect, distinct in some and non-distinct in other dialects?
In How to measure auditory distances between vowels, one chart does not mention /ɪ/ separately at all, the other one places it close to /i/.
I have few more related questions about /e ɛ/ ; /ʊ u/ and /ɑ ɔ/, which I plan to ask here, on ELL, or linguistics, depending how you will find my question be appropriate here :-)
I learned my English using [i e æ ɑ o u ʌ] vowel system, I am curious how wrong I am compared to full [i ɪ e ɛ æ ɑ ɔ o ʊ u ʌ].
Edit: I am aware about short vs long vowels (lax vs tense in proper linguistics lingo, IIUC). So my question is, if there is an important (distinguishable) difference between (short) /i/ and /ɪ/, and/or between (long) /i:/ and /ɪ:/ - if such sound as /ɪ:/ exists in English.
Also, I wanted to add "minimal-pair" tag, but none exists, not sure if it will be appropriate.