Hello Stiff (full pseudonym too long to write out)!
Nice to see some new faces (figuratively) here (actually Ive been logged in for 5 days so im not exactly ancient either)
Hope youll frequent this forum often!
As to your question, i personally think that it is easier to try a party for several reasons:
1) The experience limit in BG without addon is 89000, so your character CANNOT get more than 89000 experience points. If youre playing solo you reach that pretty early, I reached it before the end of the game with a full party.. So basically, after a certain point you CANNOT GET MORE EXPERIENCE (annoying)
2) I consider several character types almost essential for a group:
1) cleric
2) mage
3) thief
not to mention some tanks (fighters)
Its hard to combine these into one character, and it is MUCH harder to play when youre missing one of these
So anyway, Id recommend a group. Just have fun playing BG!!