Hi image132
Without knowing the conditions you'll be using the modem under, it's hard to give a definitive answer. It depends very much on the strength and quality of the LTE signal from the base station, the network operator, the amount of contention/congestion, and the ISP your sister will be using.
That said, if the station that is "close by" carries LTE equipment from the Network Operator you'll be using (Vodacom, MTN or Telkom Mobile), then chances are good that you'll get significantly faster speeds with LTE than with 3G. If I were to make a
very broad generalisation, I would say that with 3G you are likely to be below 20Mbps whereas with LTE you have the
possibility to get 30-50 Mbps or even as high as 80-90Mbps. But that depends on many other factors, too.
Bear in mind that to get the full benefit of LTE performance, the B593 has to have access to two antennas - either the two built into the B593, the two external "whips" supplied with the B593, a dual-element external antenna, or a dual-antenna array.
As regards antennas, I think it is true to say that outdoor external antennas are only
crucial if you live in an area of particularly poor signal. If you have reasonable signal anyway, you will probably do fine with just the B593's internal antennas - they're actually excellent. Personally I do think that even the most basic outdoor external antenna system will generally give you a more stable and probably slightly faster connection.
To give you
some idea of performance, I live in a built-up area with reasonable 3G and 4G presence by Vodacom, MTN and Telkom. Using the B593's built-in antenna(s), I would generally get around 10-15Mbps in 3G mode. In LTE mode, I routinely see 20-30Mbps with no particular difficulty. Switching to a highly-directional LTE antenna array gets me into the high 70's or even low 80's.
If you have some time, have a look through the
Antenna installation and alignment thread. If you have limited time, have a look at the scatter diagram in
this post to get some idea of the spread of people's LTE results so far.
You will notice that many of the results in the 30-50Mbps range were obtained with the B593's built-in antennas. There are also some excellent results in the 70-80 range (eg Biggles190) obtained in areas of good signal using just a simple dual-polarised outdoor external antenna costing about R600.
You don't say whether your sister needs mobile connectivity or whether this will be an essentially fixed installation - the B593 is intended for the latter. For a mobile installation, an LTE USB dongle would obviously be better suited.