Primarily I think that you should let yourself be guided what your immediate surroundings use. The people on the forum you intend to frequent, friends, coworkers/students, whatever they use should be an important factor in what you do. Since they are the ones you will ask questions, exchange source etc.
They might be using older versions of Delphi, Lazarus or the newest of the newest Embarcadero version. E.g. for my work, I visit electrical engineering departments a lot, and they uniformly use a Delphi 6 or 7. And if not, usually older rather than newer.
If you are gearing up to do a bit of side jobs with Delphi you have a problem. You can buy starter to learn, but as soon as you start asking money for it, you have to acquire a full license(*), and the starter license is money lost. Specially since Embarcadero recently limited the period that old versions might upgrade, you might not even get a discount on the full version because of an older starter purchase in a few years.
Besides being free, Lazarus, for educational purposes has one big advantage: the number of versions in active use is usually limited to the last two releases. This reduces versionconflicts and at worst versionitis is only temporary. This means all your peers will more or less use the same version, while with Delphi they might be scattered over more than 5-6 versions.
And of course updating lazarus is also free :-) (which is important to consider in a multi year planning, the same people urging you to buy now will urge you to get the latest and greatest in a few years too)
Personally, I think that Lazarus is fine for the initial learning and that differences that really would be a stumbling block are much further down the track. And you get a VCL/LCL path to other platforms. You can always get a Delphi version later when plans are more concrete. (either to find employment, or if you start being a self employed programmer)
(*) luckily, if I understood it right, the starter edition now allows non commercial use in foundations.