If the Israelis have more and better weapons, maybe the West Bank and Gaza, all of mandate Palestine, become part of Israel. The battles for the Jerusalem roads, Jerusalem itself, Gaza, and the southern West Bank were all grueling positional fights heavy weaponry would have made a big difference in.
This would mean a larger Nakba for sure, and weaker, angrier Arab states more concerned with dealing with the larger than OTL refugee flood. A much more confident and more heavily armed Israel, which may lead them to either 1) embark earlier on military adventurism to "deal the last blow" or 2) feel less threatened and try to ratchet down the conflict from a position of unquestioned power like a lot of Israelis on the street wanted to do post-1967.
The changes for Palestinian nationalism would be huge, with all of Palestine conquered by the Israelis, there could be a national awakening among the refugee diaspora in 1948 instead of uneasy decades spent trying to be Jordanians.
In general it would move the Arab-Israeli conflict "forward" to something resembling the 1967 power balance. How the Arab states would react to an even harder military defeat- and one given to them with a much larger element of western complicity than OTL 1948- would cause huge butterflies.
All of these reasons, it should be noted, were taken into consideration by the British OTL- they knew the military balance favored the Israelis, and they knew the Israelis (or, well, proto-Israeli militias) were trying to get heavy weaponry from the British, and they didn't want to be seen as basically handing Palestine to the Jewish militias on a plate as they left, so a lot of AFV's got driven off of cliffs, and a lot of guns got holes drilled in them.