There is no difference among kg to lb. The only difference is between calibrated and non calibrated plates. Calibrated plates are typically accurate in weight to within a few grams. Standard non calibrated are often off by a few lbs (esp 45s and 100s (lbs) or 20s 25s and 50s (kgs)). As far as different feel goes, many other things can factor into this. Being in a different gym, using different bars, and especially when lifting heavier the width of the plates can effect the whip on the bar which can all effect how heavy a given weight feels. I'm guessing these are the factors at play, not the actual weight itself.